Add mechanism to specify environment variables in kernel spec

IPython/kernel/kernelspec.py

@@ -1,112 +1,113 b''
 import io
 import json
 import os
 import sys
 
 pjoin = os.path.join
 
 from IPython.utils.path import get_ipython_dir
 from IPython.utils.py3compat import PY3
-from IPython.utils.traitlets import HasTraits, List, Unicode
+from IPython.utils.traitlets import HasTraits, List, Unicode, Dict
 
 USER_KERNEL_DIR = pjoin(get_ipython_dir(), 'kernels')
 
 if os.name == 'nt':
     programdata = os.environ.get('PROGRAMDATA', None)
     if programdata:
         SYSTEM_KERNEL_DIR = pjoin(programdata, 'ipython', 'kernels')
     else:  # PROGRAMDATA is not defined by default on XP.
         SYSTEM_KERNEL_DIR = None
 else:
     SYSTEM_KERNEL_DIR = "/usr/share/ipython/kernels"
 
 # List of kernel directories to search. Later ones take priority over earlier.
 kernel_dirs = [
     SYSTEM_KERNEL_DIR,
     USER_KERNEL_DIR,
 ]
     
 NATIVE_KERNEL_NAME = 'python3' if PY3 else 'python2'
 
 class KernelSpec(HasTraits):
     argv = List()
     display_name = Unicode()
     language = Unicode()
     codemirror_mode = None
+    env = Dict()
     
     resource_dir = Unicode()
     
     def __init__(self, resource_dir, argv, display_name, language,
                  codemirror_mode=None):
         super(KernelSpec, self).__init__(resource_dir=resource_dir, argv=argv,
                 display_name=display_name, language=language,
                 codemirror_mode=codemirror_mode)
         if not self.codemirror_mode:
             self.codemirror_mode = self.language
     
     @classmethod
     def from_resource_dir(cls, resource_dir):
         """Create a KernelSpec object by reading kernel.json
         
         Pass the path to the *directory* containing kernel.json.
         """
         kernel_file = pjoin(resource_dir, 'kernel.json')
         with io.open(kernel_file, 'r', encoding='utf-8') as f:
             kernel_dict = json.load(f)
         return cls(resource_dir=resource_dir, **kernel_dict)
 
 def _is_kernel_dir(path):
     """Is ``path`` a kernel directory?"""
     return os.path.isdir(path) and os.path.isfile(pjoin(path, 'kernel.json'))
 
 def _list_kernels_in(dir):
     """Ensure dir exists, and return a mapping of kernel names to resource
     directories from it.
     """
     if dir is None or not os.path.isdir(dir):
         return {}
     return {f.lower(): pjoin(dir, f) for f in os.listdir(dir)
                         if _is_kernel_dir(pjoin(dir, f))}
 
 def _make_native_kernel_dir():
     """Makes a kernel directory for the native kernel.
     
     The native kernel is the kernel using the same Python runtime as this
     process. This will put its informatino in the user kernels directory.
     """
     path = pjoin(USER_KERNEL_DIR, NATIVE_KERNEL_NAME)
     os.makedirs(path, mode=0o755)
     with open(pjoin(path, 'kernel.json'), 'w') as f:
         json.dump({'argv':[NATIVE_KERNEL_NAME, '-c',
                            'from IPython.kernel.zmq.kernelapp import main; main()',
                             '-f', '{connection_file}'],
                    'display_name': 'Python 3' if PY3 else 'Python 2',
                    'language': 'python',
                    'codemirror_mode': {'name': 'python',
                                        'version': sys.version_info[0]},
                   },
                   f, indent=1)
     # TODO: Copy icons into directory
     return path
 
 def find_kernel_specs():
     """Returns a dict mapping kernel names to resource directories."""
     d = {}
     for kernel_dir in kernel_dirs:
         d.update(_list_kernels_in(kernel_dir))
     
     if NATIVE_KERNEL_NAME not in d:
         d[NATIVE_KERNEL_NAME] = _make_native_kernel_dir()
     return d
     # TODO: Caching?
 
 def get_kernel_spec(kernel_name):
     """Returns a :class:`KernelSpec` instance for the given kernel_name.
     
     Raises KeyError if the given kernel name is not found.
     """
     if kernel_name == 'python':
         kernel_name = NATIVE_KERNEL_NAME
     d = find_kernel_specs()
     resource_dir = d[kernel_name.lower()]
     return KernelSpec.from_resource_dir(resource_dir)
  No newline at end of file

IPython/kernel/launcher.py

@@ -1,272 +1,256 b''
 """Utilities for launching kernels
-
-Authors:
-
-* Min Ragan-Kelley
-
 """
 
-#-----------------------------------------------------------------------------
-#  Copyright (C) 2013  The IPython Development Team
-#
-#  Distributed under the terms of the BSD License.  The full license is in
-#  the file COPYING, distributed as part of this software.
-#-----------------------------------------------------------------------------
-
-#-----------------------------------------------------------------------------
-# Imports
-#-----------------------------------------------------------------------------
+# Copyright (c) IPython Development Team.
+# Distributed under the terms of the Modified BSD License.
 
 import os
 import sys
 from subprocess import Popen, PIPE
 
 from IPython.utils.encoding import getdefaultencoding
 from IPython.utils.py3compat import cast_bytes_py2
 
-#-----------------------------------------------------------------------------
-# Launching Kernels
-#-----------------------------------------------------------------------------
 
 def swallow_argv(argv, aliases=None, flags=None):
     """strip frontend-specific aliases and flags from an argument list
     
     For use primarily in frontend apps that want to pass a subset of command-line
     arguments through to a subprocess, where frontend-specific flags and aliases
     should be removed from the list.
     
     Parameters
     ----------
     
     argv : list(str)
         The starting argv, to be filtered
     aliases : container of aliases (dict, list, set, etc.)
         The frontend-specific aliases to be removed
     flags : container of flags (dict, list, set, etc.)
         The frontend-specific flags to be removed
     
     Returns
     -------
     
     argv : list(str)
         The argv list, excluding flags and aliases that have been stripped
     """
     
     if aliases is None:
         aliases = set()
     if flags is None:
         flags = set()
     
     stripped = list(argv) # copy
     
     swallow_next = False
     was_flag = False
     for a in argv:
         if a == '--':
             break
         if swallow_next:
             swallow_next = False
             # last arg was an alias, remove the next one
             # *unless* the last alias has a no-arg flag version, in which
             # case, don't swallow the next arg if it's also a flag:
             if not (was_flag and a.startswith('-')):
                 stripped.remove(a)
                 continue
         if a.startswith('-'):
             split = a.lstrip('-').split('=')
             name = split[0]
             # we use startswith because argparse accepts any arg to be specified
             # by any leading section, as long as it is unique,
             # so `--no-br` means `--no-browser` in the notebook, etc.
             if any(alias.startswith(name) for alias in aliases):
                 stripped.remove(a)
                 if len(split) == 1:
                     # alias passed with arg via space
                     swallow_next = True
                     # could have been a flag that matches an alias, e.g. `existing`
                     # in which case, we might not swallow the next arg
                     was_flag = name in flags
             elif len(split) == 1 and any(flag.startswith(name) for flag in flags):
                 # strip flag, but don't swallow next, as flags don't take args
                 stripped.remove(a)
     
     # return shortened list
     return stripped
 
 
 def make_ipkernel_cmd(code, executable=None, extra_arguments=[], **kw):
     """Build Popen command list for launching an IPython kernel.
 
     Parameters
     ----------
     code : str,
         A string of Python code that imports and executes a kernel entry point.
 
     executable : str, optional (default sys.executable)
         The Python executable to use for the kernel process.
 
     extra_arguments : list, optional
         A list of extra arguments to pass when executing the launch code.
     
     Returns
     -------
     
     A Popen command list
     """
     
     # Build the kernel launch command.
     if executable is None:
         executable = sys.executable
     arguments = [ executable, '-c', code, '-f', '{connection_file}' ]
     arguments.extend(extra_arguments)
 
     # Spawn a kernel.
     if sys.platform == 'win32':
 
         # If the kernel is running on pythonw and stdout/stderr are not been
         # re-directed, it will crash when more than 4KB of data is written to
         # stdout or stderr. This is a bug that has been with Python for a very
         # long time; see http://bugs.python.org/issue706263.
         # A cleaner solution to this problem would be to pass os.devnull to
         # Popen directly. Unfortunately, that does not work.
         if executable.endswith('pythonw.exe'):
             arguments.append('--no-stdout')
             arguments.append('--no-stderr')
 
     return arguments
 
 
-def launch_kernel(cmd, stdin=None, stdout=None, stderr=None,
+def launch_kernel(cmd, stdin=None, stdout=None, stderr=None, env=None,
                         independent=False,
                         cwd=None, ipython_kernel=True,
                         **kw
                         ):
     """ Launches a localhost kernel, binding to the specified ports.
 
     Parameters
     ----------
     cmd : Popen list,
         A string of Python code that imports and executes a kernel entry point.
 
     stdin, stdout, stderr : optional (default None)
         Standards streams, as defined in subprocess.Popen.
 
     independent : bool, optional (default False)
         If set, the kernel process is guaranteed to survive if this process
         dies. If not set, an effort is made to ensure that the kernel is killed
         when this process dies. Note that in this case it is still good practice
         to kill kernels manually before exiting.
 
     cwd : path, optional
         The working dir of the kernel process (default: cwd of this process).
 
     ipython_kernel : bool, optional
         Whether the kernel is an official IPython one,
         and should get a bit of special treatment.
 
     Returns
     -------
     
     Popen instance for the kernel subprocess
     """
 
     # Popen will fail (sometimes with a deadlock) if stdin, stdout, and stderr
     # are invalid. Unfortunately, there is in general no way to detect whether
     # they are valid.  The following two blocks redirect them to (temporary)
     # pipes in certain important cases.
 
     # If this process has been backgrounded, our stdin is invalid. Since there
     # is no compelling reason for the kernel to inherit our stdin anyway, we'll
     # place this one safe and always redirect.
     redirect_in = True
     _stdin = PIPE if stdin is None else stdin
 
     # If this process in running on pythonw, we know that stdin, stdout, and
     # stderr are all invalid.
     redirect_out = sys.executable.endswith('pythonw.exe')
     if redirect_out:
         _stdout = PIPE if stdout is None else stdout
         _stderr = PIPE if stderr is None else stderr
     else:
         _stdout, _stderr = stdout, stderr
     
     encoding = getdefaultencoding(prefer_stream=False)
     
     # Spawn a kernel.
     if sys.platform == 'win32':
         # Popen on Python 2 on Windows cannot handle unicode args or cwd
         cmd = [ cast_bytes_py2(c, encoding) for c in cmd ]
         if cwd:
             cwd = cast_bytes_py2(cwd, sys.getfilesystemencoding() or 'ascii')
         
         from IPython.kernel.zmq.parentpoller import ParentPollerWindows
         # Create a Win32 event for interrupting the kernel.
         interrupt_event = ParentPollerWindows.create_interrupt_event()
         if ipython_kernel:
             cmd += [ '--interrupt=%i' % interrupt_event ]
 
             # If the kernel is running on pythonw and stdout/stderr are not been
             # re-directed, it will crash when more than 4KB of data is written to
             # stdout or stderr. This is a bug that has been with Python for a very
             # long time; see http://bugs.python.org/issue706263.
             # A cleaner solution to this problem would be to pass os.devnull to
             # Popen directly. Unfortunately, that does not work.
             if cmd[0].endswith('pythonw.exe'):
                 if stdout is None:
                     cmd.append('--no-stdout')
                 if stderr is None:
                     cmd.append('--no-stderr')
 
         # Launch the kernel process.
         if independent:
             proc = Popen(cmd,
                          creationflags=512, # CREATE_NEW_PROCESS_GROUP
-                         stdin=_stdin, stdout=_stdout, stderr=_stderr, env=os.environ)
+                         stdin=_stdin, stdout=_stdout, stderr=_stderr, env=env)
         else:
             if ipython_kernel:
                 try:
                     from _winapi import DuplicateHandle, GetCurrentProcess, \
                         DUPLICATE_SAME_ACCESS
                 except:
                     from _subprocess import DuplicateHandle, GetCurrentProcess, \
                         DUPLICATE_SAME_ACCESS
                 pid = GetCurrentProcess()
                 handle = DuplicateHandle(pid, pid, pid, 0,
                                          True, # Inheritable by new processes.
                                          DUPLICATE_SAME_ACCESS)
                 cmd +=[ '--parent=%i' % handle ]
             
             
             proc = Popen(cmd,
-                         stdin=_stdin, stdout=_stdout, stderr=_stderr, cwd=cwd, env=os.environ)
+                         stdin=_stdin, stdout=_stdout, stderr=_stderr, cwd=cwd, env=env)
 
         # Attach the interrupt event to the Popen objet so it can be used later.
         proc.win32_interrupt_event = interrupt_event
 
     else:
         if independent:
             proc = Popen(cmd, preexec_fn=lambda: os.setsid(),
-                         stdin=_stdin, stdout=_stdout, stderr=_stderr, cwd=cwd, env=os.environ)
+                         stdin=_stdin, stdout=_stdout, stderr=_stderr, cwd=cwd, env=env)
         else:
             if ipython_kernel:
                 cmd += ['--parent=1']
             proc = Popen(cmd,
-                         stdin=_stdin, stdout=_stdout, stderr=_stderr, cwd=cwd, env=os.environ)
+                         stdin=_stdin, stdout=_stdout, stderr=_stderr, cwd=cwd, env=env)
 
     # Clean up pipes created to work around Popen bug.
     if redirect_in:
         if stdin is None:
             proc.stdin.close()
     if redirect_out:
         if stdout is None:
             proc.stdout.close()
         if stderr is None:
             proc.stderr.close()
 
     return proc
 
 __all__ = [
     'swallow_argv',
     'make_ipkernel_cmd',
     'launch_kernel',
 ]

IPython/kernel/manager.py

@@ -1,410 +1,403 b''
 """Base class to manage a running kernel"""
 
-#-----------------------------------------------------------------------------
-#  Copyright (C) 2013  The IPython Development Team
-#
-#  Distributed under the terms of the BSD License.  The full license is in
-#  the file COPYING, distributed as part of this software.
-#-----------------------------------------------------------------------------
-
-#-----------------------------------------------------------------------------
-# Imports
-#-----------------------------------------------------------------------------
+# Copyright (c) IPython Development Team.
+# Distributed under the terms of the Modified BSD License.
 
 from __future__ import absolute_import
 
 # Standard library imports
+import os
 import re
 import signal
 import sys
 import time
 import warnings
 
 import zmq
 
 # Local imports
 from IPython.config.configurable import LoggingConfigurable
 from IPython.utils.importstring import import_item
 from IPython.utils.localinterfaces import is_local_ip, local_ips
 from IPython.utils.traitlets import (
     Any, Instance, Unicode, List, Bool, Type, DottedObjectName
 )
 from IPython.kernel import (
     make_ipkernel_cmd,
     launch_kernel,
     kernelspec,
 )
 from .connect import ConnectionFileMixin
 from .zmq.session import Session
 from .managerabc import (
     KernelManagerABC
 )
 
-#-----------------------------------------------------------------------------
-# Main kernel manager class
-#-----------------------------------------------------------------------------
 
 class KernelManager(LoggingConfigurable, ConnectionFileMixin):
     """Manages a single kernel in a subprocess on this host.
 
     This version starts kernels with Popen.
     """
 
     # The PyZMQ Context to use for communication with the kernel.
     context = Instance(zmq.Context)
     def _context_default(self):
         return zmq.Context.instance()
 
     # The Session to use for communication with the kernel.
     session = Instance(Session)
     def _session_default(self):
         return Session(parent=self)
 
     # the class to create with our `client` method
     client_class = DottedObjectName('IPython.kernel.blocking.BlockingKernelClient')
     client_factory = Type()
     def _client_class_changed(self, name, old, new):
         self.client_factory = import_item(str(new))
 
     # The kernel process with which the KernelManager is communicating.
     # generally a Popen instance
     kernel = Any()
     
     kernel_name = Unicode('python')
     
     kernel_spec = Instance(kernelspec.KernelSpec)
     
     def _kernel_spec_default(self):
         return kernelspec.get_kernel_spec(self.kernel_name)
     
     def _kernel_name_changed(self, name, old, new):
         self.kernel_spec = kernelspec.get_kernel_spec(new)
         self.ipython_kernel = new in {'python', 'python2', 'python3'}
 
     kernel_cmd = List(Unicode, config=True,
         help="""DEPRECATED: Use kernel_name instead.
         
         The Popen Command to launch the kernel.
         Override this if you have a custom kernel.
         If kernel_cmd is specified in a configuration file,
         IPython does not pass any arguments to the kernel,
         because it cannot make any assumptions about the 
         arguments that the kernel understands. In particular,
         this means that the kernel does not receive the
         option --debug if it given on the IPython command line.
         """
     )
 
     def _kernel_cmd_changed(self, name, old, new):
         warnings.warn("Setting kernel_cmd is deprecated, use kernel_spec to "
                       "start different kernels.")
         self.ipython_kernel = False
 
     ipython_kernel = Bool(True)
 
     # Protected traits
     _launch_args = Any()
     _control_socket = Any()
 
     _restarter = Any()
 
     autorestart = Bool(False, config=True,
         help="""Should we autorestart the kernel if it dies."""
     )
 
     def __del__(self):
         self._close_control_socket()
         self.cleanup_connection_file()
 
     #--------------------------------------------------------------------------
     # Kernel restarter
     #--------------------------------------------------------------------------
 
     def start_restarter(self):
         pass
 
     def stop_restarter(self):
         pass
 
     def add_restart_callback(self, callback, event='restart'):
         """register a callback to be called when a kernel is restarted"""
         if self._restarter is None:
             return
         self._restarter.add_callback(callback, event)
 
     def remove_restart_callback(self, callback, event='restart'):
         """unregister a callback to be called when a kernel is restarted"""
         if self._restarter is None:
             return
         self._restarter.remove_callback(callback, event)
 
     #--------------------------------------------------------------------------
     # create a Client connected to our Kernel
     #--------------------------------------------------------------------------
 
     def client(self, **kwargs):
         """Create a client configured to connect to our kernel"""
         if self.client_factory is None:
             self.client_factory = import_item(self.client_class)
 
         kw = {}
         kw.update(self.get_connection_info())
         kw.update(dict(
             connection_file=self.connection_file,
             session=self.session,
             parent=self,
         ))
 
         # add kwargs last, for manual overrides
         kw.update(kwargs)
         return self.client_factory(**kw)
 
     #--------------------------------------------------------------------------
     # Kernel management
     #--------------------------------------------------------------------------
 
     def format_kernel_cmd(self, **kw):
         """replace templated args (e.g. {connection_file})"""
         if self.kernel_cmd:
             cmd = self.kernel_cmd
         elif self.kernel_name == 'python':
             # The native kernel gets special handling
             cmd = make_ipkernel_cmd(
                 'from IPython.kernel.zmq.kernelapp import main; main()',
                 **kw
             )
         else:
             cmd = self.kernel_spec.argv
 
         ns = dict(connection_file=self.connection_file)
         ns.update(self._launch_args)
         
         pat = re.compile(r'\{([A-Za-z0-9_]+)\}')
         def from_ns(match):
             """Get the key out of ns if it's there, otherwise no change."""
             return ns.get(match.group(1), match.group())
         
         return [ pat.sub(from_ns, arg) for arg in cmd ]
 
     def _launch_kernel(self, kernel_cmd, **kw):
         """actually launch the kernel
 
         override in a subclass to launch kernel subprocesses differently
         """
         return launch_kernel(kernel_cmd, **kw)
 
     # Control socket used for polite kernel shutdown
 
     def _connect_control_socket(self):
         if self._control_socket is None:
             self._control_socket = self.connect_control()
             self._control_socket.linger = 100
 
     def _close_control_socket(self):
         if self._control_socket is None:
             return
         self._control_socket.close()
         self._control_socket = None
 
     def start_kernel(self, **kw):
         """Starts a kernel on this host in a separate process.
 
         If random ports (port=0) are being used, this method must be called
         before the channels are created.
 
         Parameters
         ----------
         **kw : optional
              keyword arguments that are passed down to build the kernel_cmd
              and launching the kernel (e.g. Popen kwargs).
         """
         if self.transport == 'tcp' and not is_local_ip(self.ip):
             raise RuntimeError("Can only launch a kernel on a local interface. "
                                "Make sure that the '*_address' attributes are "
                                "configured properly. "
                                "Currently valid addresses are: %s" % local_ips()
                                )
 
         # write connection file / get default ports
         self.write_connection_file()
 
         # save kwargs for use in restart
         self._launch_args = kw.copy()
         # build the Popen cmd
         kernel_cmd = self.format_kernel_cmd(**kw)
+        if self.kernel_cmd:
+            # If kernel_cmd has been set manually, don't refer to a kernel spec
+            env = os.environ
+        else:
+            # Environment variables from kernel spec are added to os.environ
+            env = os.environ.copy()
+            env.update(self.kernel_spec.env or {})
         # launch the kernel subprocess
-        self.kernel = self._launch_kernel(kernel_cmd,
+        self.kernel = self._launch_kernel(kernel_cmd, env=env,
                                     ipython_kernel=self.ipython_kernel,
                                     **kw)
         self.start_restarter()
         self._connect_control_socket()
 
     def _send_shutdown_request(self, restart=False):
         """TODO: send a shutdown request via control channel"""
         content = dict(restart=restart)
         msg = self.session.msg("shutdown_request", content=content)
         self.session.send(self._control_socket, msg)
 
     def shutdown_kernel(self, now=False, restart=False):
         """Attempts to the stop the kernel process cleanly.
 
         This attempts to shutdown the kernels cleanly by:
 
         1. Sending it a shutdown message over the shell channel.
         2. If that fails, the kernel is shutdown forcibly by sending it
            a signal.
 
         Parameters
         ----------
         now : bool
             Should the kernel be forcible killed *now*. This skips the
             first, nice shutdown attempt.
         restart: bool
             Will this kernel be restarted after it is shutdown. When this
             is True, connection files will not be cleaned up.
         """
         # Stop monitoring for restarting while we shutdown.
         self.stop_restarter()
 
         # FIXME: Shutdown does not work on Windows due to ZMQ errors!
         if now or sys.platform == 'win32':
             if self.has_kernel:
                 self._kill_kernel()
         else:
             # Don't send any additional kernel kill messages immediately, to give
             # the kernel a chance to properly execute shutdown actions. Wait for at
             # most 1s, checking every 0.1s.
             self._send_shutdown_request(restart=restart)
             for i in range(10):
                 if self.is_alive():
                     time.sleep(0.1)
                 else:
                     break
             else:
                 # OK, we've waited long enough.
                 if self.has_kernel:
                     self._kill_kernel()
 
         if not restart:
             self.cleanup_connection_file()
             self.cleanup_ipc_files()
         else:
             self.cleanup_ipc_files()
         
         self._close_control_socket()
 
     def restart_kernel(self, now=False, **kw):
         """Restarts a kernel with the arguments that were used to launch it.
 
         If the old kernel was launched with random ports, the same ports will be
         used for the new kernel. The same connection file is used again.
 
         Parameters
         ----------
         now : bool, optional
             If True, the kernel is forcefully restarted *immediately*, without
             having a chance to do any cleanup action.  Otherwise the kernel is
             given 1s to clean up before a forceful restart is issued.
 
             In all cases the kernel is restarted, the only difference is whether
             it is given a chance to perform a clean shutdown or not.
 
         **kw : optional
             Any options specified here will overwrite those used to launch the
             kernel.
         """
         if self._launch_args is None:
             raise RuntimeError("Cannot restart the kernel. "
                                "No previous call to 'start_kernel'.")
         else:
             # Stop currently running kernel.
             self.shutdown_kernel(now=now, restart=True)
 
             # Start new kernel.
             self._launch_args.update(kw)
             self.start_kernel(**self._launch_args)
 
             # FIXME: Messages get dropped in Windows due to probable ZMQ bug
             # unless there is some delay here.
             if sys.platform == 'win32':
                 time.sleep(0.2)
 
     @property
     def has_kernel(self):
         """Has a kernel been started that we are managing."""
         return self.kernel is not None
 
     def _kill_kernel(self):
         """Kill the running kernel.
 
         This is a private method, callers should use shutdown_kernel(now=True).
         """
         if self.has_kernel:
 
             # Signal the kernel to terminate (sends SIGKILL on Unix and calls
             # TerminateProcess() on Win32).
             try:
                 self.kernel.kill()
             except OSError as e:
                 # In Windows, we will get an Access Denied error if the process
                 # has already terminated. Ignore it.
                 if sys.platform == 'win32':
                     if e.winerror != 5:
                         raise
                 # On Unix, we may get an ESRCH error if the process has already
                 # terminated. Ignore it.
                 else:
                     from errno import ESRCH
                     if e.errno != ESRCH:
                         raise
 
             # Block until the kernel terminates.
             self.kernel.wait()
             self.kernel = None
         else:
             raise RuntimeError("Cannot kill kernel. No kernel is running!")
 
     def interrupt_kernel(self):
         """Interrupts the kernel by sending it a signal.
 
         Unlike ``signal_kernel``, this operation is well supported on all
         platforms.
         """
         if self.has_kernel:
             if sys.platform == 'win32':
                 from .zmq.parentpoller import ParentPollerWindows as Poller
                 Poller.send_interrupt(self.kernel.win32_interrupt_event)
             else:
                 self.kernel.send_signal(signal.SIGINT)
         else:
             raise RuntimeError("Cannot interrupt kernel. No kernel is running!")
 
     def signal_kernel(self, signum):
         """Sends a signal to the kernel.
 
         Note that since only SIGTERM is supported on Windows, this function is
         only useful on Unix systems.
         """
         if self.has_kernel:
             self.kernel.send_signal(signum)
         else:
             raise RuntimeError("Cannot signal kernel. No kernel is running!")
 
     def is_alive(self):
         """Is the kernel process still running?"""
         if self.has_kernel:
             if self.kernel.poll() is None:
                 return True
             else:
                 return False
         else:
             # we don't have a kernel
             return False
 
 
-#-----------------------------------------------------------------------------
-# ABC Registration
-#-----------------------------------------------------------------------------
-
 KernelManagerABC.register(KernelManager)