py3: implement __bytes__() on most of our exception classes

We store bytes in exc.args, which should be translated to a byte string
without encode/decode dance.

IOError subclasses are unchanged for now. We'll need to decide how our
IOErrors should be caught.

mercurial/error.py

@@ -13,7 +13,16 imports.
 
 from __future__ import absolute_import
 
-# Do not import anything here, please
+# Do not import anything but pycompat here, please
+from . import pycompat
+
+def _tobytes(exc):
+    """Byte-stringify exception in the same way as BaseException_str()"""
+    if not exc.args:
+        return b''
+    if len(exc.args) == 1:
+        return pycompat.bytestr(exc.args[0])
+    return b'(%s)' % b', '.join(b"'%s'" % pycompat.bytestr(a) for a in exc.args)
 
 class Hint(object):
     """Mix-in to provide a hint of an error
@@ -26,10 +35,10 class Hint(object):
         super(Hint, self).__init__(*args, **kw)
 
 class RevlogError(Hint, Exception):
-    pass
+    __bytes__ = _tobytes
 
 class FilteredIndexError(IndexError):
-    pass
+    __bytes__ = _tobytes
 
 class LookupError(RevlogError, KeyError):
     def __init__(self, name, index, message):
@@ -43,6 +52,9 class LookupError(RevlogError, KeyError)
             name = short(name)
         RevlogError.__init__(self, '%s@%s: %s' % (index, name, message))
 
+    def __bytes__(self):
+        return RevlogError.__bytes__(self)
+
     def __str__(self):
         return RevlogError.__str__(self)
 
@@ -54,12 +66,15 class ManifestLookupError(LookupError):
 
 class CommandError(Exception):
     """Exception raised on errors in parsing the command line."""
+    __bytes__ = _tobytes
 
 class InterventionRequired(Hint, Exception):
     """Exception raised when a command requires human intervention."""
+    __bytes__ = _tobytes
 
 class Abort(Hint, Exception):
     """Raised if a command needs to print an error and exit."""
+    __bytes__ = _tobytes
 
 class HookLoadError(Abort):
     """raised when loading a hook fails, aborting an operation
@@ -94,9 +109,11 class ResponseExpected(Abort):
 
 class OutOfBandError(Hint, Exception):
     """Exception raised when a remote repo reports failure"""
+    __bytes__ = _tobytes
 
 class ParseError(Hint, Exception):
     """Raised when parsing config files and {rev,file}sets (msg[, pos])"""
+    __bytes__ = _tobytes
 
 class UnknownIdentifier(ParseError):
     """Exception raised when a {rev,file}set references an unknown identifier"""
@@ -108,7 +125,7 class UnknownIdentifier(ParseError):
         self.symbols = symbols
 
 class RepoError(Hint, Exception):
-    pass
+    __bytes__ = _tobytes
 
 class RepoLookupError(RepoError):
     pass
@@ -128,6 +145,8 class StdioError(IOError):
     def __init__(self, err):
         IOError.__init__(self, err.errno, err.strerror)
 
+    # no __bytes__() because error message is derived from the standard IOError
+
 class UnsupportedMergeRecords(Abort):
     def __init__(self, recordtypes):
         from .i18n import _
@@ -151,6 +170,8 class LockError(IOError):
         IOError.__init__(self, errno, strerror, filename)
         self.desc = desc
 
+    # no __bytes__() because error message is derived from the standard IOError
+
 class LockHeld(LockError):
     def __init__(self, errno, filename, desc, locker):
         LockError.__init__(self, errno, 'Lock held', filename, desc)
@@ -161,36 +182,43 class LockUnavailable(LockError):
 
 # LockError is for errors while acquiring the lock -- this is unrelated
 class LockInheritanceContractViolation(RuntimeError):
-    pass
+    __bytes__ = _tobytes
 
 class ResponseError(Exception):
     """Raised to print an error with part of output and exit."""
+    __bytes__ = _tobytes
 
 class UnknownCommand(Exception):
     """Exception raised if command is not in the command table."""
+    __bytes__ = _tobytes
 
 class AmbiguousCommand(Exception):
     """Exception raised if command shortcut matches more than one command."""
+    __bytes__ = _tobytes
 
 # derived from KeyboardInterrupt to simplify some breakout code
 class SignalInterrupt(KeyboardInterrupt):
     """Exception raised on SIGTERM and SIGHUP."""
 
 class SignatureError(Exception):
-    pass
+    __bytes__ = _tobytes
 
 class PushRaced(RuntimeError):
     """An exception raised during unbundling that indicate a push race"""
+    __bytes__ = _tobytes
 
 class ProgrammingError(Hint, RuntimeError):
     """Raised if a mercurial (core or extension) developer made a mistake"""
+    __bytes__ = _tobytes
 
 class WdirUnsupported(Exception):
     """An exception which is raised when 'wdir()' is not supported"""
+    __bytes__ = _tobytes
 
 # bundle2 related errors
 class BundleValueError(ValueError):
     """error raised when bundle2 cannot be processed"""
+    __bytes__ = _tobytes
 
 class BundleUnknownFeatureError(BundleValueError):
     def __init__(self, parttype=None, params=(), values=()):
@@ -217,6 +245,7 class BundleUnknownFeatureError(BundleVa
 
 class ReadOnlyPartError(RuntimeError):
     """error raised when code tries to alter a part being generated"""
+    __bytes__ = _tobytes
 
 class PushkeyFailed(Abort):
     """error raised when a pushkey part failed to update a value"""
@@ -257,12 +286,15 class InvalidBundleSpecification(Excepti
 
     This is used for syntax errors as opposed to support errors.
     """
+    __bytes__ = _tobytes
 
 class UnsupportedBundleSpecification(Exception):
     """error raised when a bundle specification is not supported."""
+    __bytes__ = _tobytes
 
 class CorruptedState(Exception):
     """error raised when a command is not able to read its state from file"""
+    __bytes__ = _tobytes
 
 class PeerTransportError(Abort):
     """Transport-level I/O error when communicating with a peer repo."""

tests/test-py3-commands.t

@@ -151,6 +151,11 Test weird unicode-vs-bytes stuff
   options ([+] can be repeated):
   (some details hidden, use --verbose to show complete help)
 
+  $ $PYTHON3 $HGBIN help -k notopic
+  abort: no matches
+  (try 'hg help' for a list of topics)
+  [255]
+
 Prove the repo is valid using the Python 2 `hg`:
   $ hg verify
   checking changesets