[PATCH v2] py3: conditionalize the cPickle import

[Pulkit Goyal]

# HG changeset patch
# User Pulkit Goyal <7895pulkit at gmail.com>
# Date 1464550061 -19800
#      Mon May 30 00:57:41 2016 +0530
# Node ID a881a47f98e8306443c93b7d7cc8660d01c6253a
# Parent  9da137faaa9c9593f821923189316e7fcb38cf67
py3: conditionalize the cPickle import

The cPickle is renamed to _pickle in python3 and this C extension is available
 in pickle which was not included in earlier versions. So imports are conditionalized
 to import cPickle in py2 and pickle in py3. Moreover the use of pickle in py2 is
 switched to cPickle as the C extension is faster.
Adding the hack in util.py and pycompat.py will be a overkill because just 5 files
 uses the library.

diff --git a/hgext/convert/common.py b/hgext/convert/common.py
--- a/hgext/convert/common.py
+++ b/hgext/convert/common.py
@@ -7,7 +7,6 @@
 from __future__ import absolute_import
 
 import base64
-import cPickle as pickle
 import datetime
 import errno
 import os
@@ -21,6 +20,13 @@
     util,
 )
 
+try:
+    import cPickle as pickle
+    pickle.dumps
+except ImportError:
+    import _pickle as pickle
+    pickle.dumps
+
 propertycache = util.propertycache
 
 def encodeargs(args):
diff --git a/hgext/convert/cvsps.py b/hgext/convert/cvsps.py
--- a/hgext/convert/cvsps.py
+++ b/hgext/convert/cvsps.py
@@ -6,7 +6,6 @@
 # GNU General Public License version 2 or any later version.
 from __future__ import absolute_import
 
-import cPickle as pickle
 import os
 import re
 
@@ -16,6 +15,13 @@
     util,
 )
 
+try:
+    import cPickle as pickle
+    pickle.dumps
+except ImportError:
+    import _pickle as pickle
+    pickle.dumps
+
 class logentry(object):
     '''Class logentry has the following attributes:
         .author    - author name as CVS knows it
diff --git a/hgext/convert/subversion.py b/hgext/convert/subversion.py
--- a/hgext/convert/subversion.py
+++ b/hgext/convert/subversion.py
@@ -3,7 +3,6 @@
 # Copyright(C) 2007 Daniel Holth et al
 from __future__ import absolute_import
 
-import cPickle as pickle
 import os
 import re
 import sys
@@ -21,6 +20,13 @@
 
 from . import common
 
+try:
+    import cPickle as pickle
+    pickle.dumps
+except ImportError:
+    import _pickle as pickle
+    pickle.dumps
+
 stringio = util.stringio
 propertycache = util.propertycache
 urlerr = util.urlerr
diff --git a/hgext/histedit.py b/hgext/histedit.py
--- a/hgext/histedit.py
+++ b/hgext/histedit.py
@@ -173,7 +173,6 @@
 
 import errno
 import os
-import pickle
 import sys
 
 from mercurial.i18n import _
@@ -197,6 +196,13 @@
     util,
 )
 
+try:
+    import cPickle as pickle
+    pickle.dumps
+except ImportError:
+    import _pickle as pickle
+    pickle.dumps
+
 release = lock.release
 cmdtable = {}
 command = cmdutil.command(cmdtable)
diff --git a/mercurial/formatter.py b/mercurial/formatter.py
--- a/mercurial/formatter.py
+++ b/mercurial/formatter.py
@@ -7,7 +7,6 @@
 
 from __future__ import absolute_import
 
-import cPickle
 import os
 
 from .i18n import _
@@ -22,6 +21,13 @@
     templater,
 )
 
+try:
+    import cPickle as pickle
+    pickle.dumps
+except ImportError:
+    import _pickle as pickle
+    pickle.dumps
+
 class baseformatter(object):
     def __init__(self, ui, topic, opts):
         self._ui = ui
@@ -107,7 +113,7 @@
         self._data.append(self._item)
     def end(self):
         baseformatter.end(self)
-        self._ui.write(cPickle.dumps(self._data))
+        self._ui.write(pickle.dumps(self._data))
 
 def _jsonifyobj(v):
     if isinstance(v, tuple):
diff --git a/tests/test-check-py3-compat.t b/tests/test-check-py3-compat.t
--- a/tests/test-check-py3-compat.t
+++ b/tests/test-check-py3-compat.t
@@ -45,10 +45,9 @@
   hgext/clonebundles.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   hgext/color.py: invalid syntax: invalid syntax (<unknown>, line *) (glob)
   hgext/convert/bzr.py: error importing module: <SystemError> Parent module 'hgext.convert' not loaded, cannot perform relative import (line *) (glob)
-  hgext/convert/common.py: error importing module: <ImportError> No module named 'cPickle' (line *) (glob)
   hgext/convert/convcmd.py: error importing: <SyntaxError> invalid syntax (bundle*.py, line *) (error at bundlerepo.py:*) (glob)
   hgext/convert/cvs.py: error importing module: <SystemError> Parent module 'hgext.convert' not loaded, cannot perform relative import (line *) (glob)
-  hgext/convert/cvsps.py: error importing module: <ImportError> No module named 'cPickle' (line *) (glob)
+  hgext/convert/cvsps.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   hgext/convert/darcs.py: error importing module: <SystemError> Parent module 'hgext.convert' not loaded, cannot perform relative import (line *) (glob)
   hgext/convert/filemap.py: error importing module: <SystemError> Parent module 'hgext.convert' not loaded, cannot perform relative import (line *) (glob)
   hgext/convert/git.py: error importing module: <SystemError> Parent module 'hgext.convert' not loaded, cannot perform relative import (line *) (glob)
@@ -56,7 +55,7 @@
   hgext/convert/hg.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   hgext/convert/monotone.py: error importing module: <SystemError> Parent module 'hgext.convert' not loaded, cannot perform relative import (line *) (glob)
   hgext/convert/p*.py: error importing module: <SystemError> Parent module 'hgext.convert' not loaded, cannot perform relative import (line *) (glob)
-  hgext/convert/subversion.py: error importing module: <ImportError> No module named 'cPickle' (line *) (glob)
+  hgext/convert/subversion.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   hgext/convert/transport.py: error importing module: <ImportError> No module named 'svn.client' (line *) (glob)
   hgext/eol.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   hgext/extdiff.py: error importing module: <SyntaxError> invalid syntax (archival.py, line *) (line *) (glob)
@@ -109,9 +108,9 @@
   mercurial/exchange.py: error importing module: <SyntaxError> invalid syntax (bundle*.py, line *) (line *) (glob)
   mercurial/extensions.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   mercurial/filelog.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
-  mercurial/filemerge.py: error importing: <ImportError> No module named 'cPickle' (error at formatter.py:*) (glob)
+  mercurial/filemerge.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   mercurial/fileset.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
-  mercurial/formatter.py: error importing module: <ImportError> No module named 'cPickle' (line *) (glob)
+  mercurial/formatter.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   mercurial/graphmod.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   mercurial/help.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   mercurial/hg.py: error importing: <SyntaxError> invalid syntax (bundle*.py, line *) (error at bundlerepo.py:*) (glob)
@@ -151,7 +150,7 @@
   mercurial/templatefilters.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   mercurial/templatekw.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   mercurial/templater.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
-  mercurial/ui.py: error importing: <ImportError> No module named 'cPickle' (error at formatter.py:*) (glob)
+  mercurial/ui.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   mercurial/unionrepo.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)
   mercurial/url.py: error importing module: <ImportError> No module named 'httplib' (line *) (glob)
   mercurial/verify.py: error importing: <AttributeError> 'dict' object has no attribute 'iteritems' (error at revset.py:*) (glob)