Don't rely on `get_ipython` in builtins in library code

IPython/core/completerlib.py

@@ -33,7 +33,7 b' from IPython.core.error import TryNext'
 from IPython.utils._process_common import arg_split
 
 # FIXME: this should be pulled in with the right call via the component system
-from IPython.core.ipapi import get as get_ipython
+from IPython import get_ipython
 
 #-----------------------------------------------------------------------------
 # Globals and constants

IPython/core/debugger.py

@@ -31,6 +31,7 b' import functools'
 import linecache
 import sys
 
+from IPython import get_ipython
 from IPython.utils import PyColorize, ulinecache
 from IPython.core import ipapi
 from IPython.utils import coloransi, io, py3compat
@@ -113,9 +114,8 b' class Tracer(object):'
         from the Python standard library for usage details.
         """
 
-        try:
-            ip = get_ipython()
-        except NameError:
+        ip = get_ipython()
+        if ip is None:
             # Outside of ipython, we set our own exception hook manually
             sys.excepthook = functools.partial(BdbQuit_excepthook,
                                                excepthook=sys.excepthook)

IPython/lib/backgroundjobs.py

@@ -33,6 +33,7 b' use of the system.'
 import sys
 import threading
 
+from IPython import get_ipython
 from IPython.core.ultratb import AutoFormattedTB
 from IPython.utils.warn import error
 

IPython/lib/editorhooks.py

@@ -8,6 +8,8 b' Contributions are *very* welcome.'
 import os
 import pipes
 import subprocess
+
+from IPython import get_ipython
 from IPython.core.error import TryNext