py3: conditionalize _winreg import

py3: conditionalize _winreg import

_winreg module is renamed to winreg in python 3. Added the conditionalize
statements in the respective file because adding this in pycompat will result
in pycompat throwing error as this is a windows registry module and we have
buildbots and most of the contributors on linux.

--- a/mercurial/scmwindows.py	Mon Aug 08 23:51:11 2016 +0530
+++ b/mercurial/scmwindows.py	Wed Aug 10 04:35:44 2016 +0530
@@ -1,6 +1,5 @@
 from __future__ import absolute_import
 
-import _winreg
 import os
 
 from . import (
@@ -8,6 +7,12 @@
     util,
 )
 
+try:
+    import _winreg as winreg
+    winreg.CloseKey
+except ImportError:
+    import winreg
+
 def systemrcpath():
     '''return default os-specific hgrc search path'''
     rcpath = []
@@ -23,7 +28,7 @@
                 rcpath.append(os.path.join(progrcd, f))
     # else look for a system rcpath in the registry
     value = util.lookupreg('SOFTWARE\\Mercurial', None,
-                           _winreg.HKEY_LOCAL_MACHINE)
+                           winreg.HKEY_LOCAL_MACHINE)
     if not isinstance(value, str) or not value:
         return rcpath
     value = util.localpath(value)

--- a/mercurial/windows.py	Mon Aug 08 23:51:11 2016 +0530
+++ b/mercurial/windows.py	Wed Aug 10 04:35:44 2016 +0530
@@ -7,7 +7,6 @@
 
 from __future__ import absolute_import
 
-import _winreg
 import errno
 import msvcrt
 import os
@@ -22,6 +21,12 @@
     win32,
 )
 
+try:
+    import _winreg as winreg
+    winreg.CloseKey
+except ImportError:
+    import winreg
+
 executablepath = win32.executablepath
 getuser = win32.getuser
 hidewindow = win32.hidewindow
@@ -432,12 +437,12 @@
     LOCAL_MACHINE).
     '''
     if scope is None:
-        scope = (_winreg.HKEY_CURRENT_USER, _winreg.HKEY_LOCAL_MACHINE)
+        scope = (winreg.HKEY_CURRENT_USER, winreg.HKEY_LOCAL_MACHINE)
     elif not isinstance(scope, (list, tuple)):
         scope = (scope,)
     for s in scope:
         try:
-            val = _winreg.QueryValueEx(_winreg.OpenKey(s, key), valname)[0]
+            val = winreg.QueryValueEx(winreg.OpenKey(s, key), valname)[0]
             # never let a Unicode string escape into the wild
             return encoding.tolocal(val.encode('UTF-8'))
         except EnvironmentError:

--- a/tests/test-check-py3-compat.t	Mon Aug 08 23:51:11 2016 +0530
+++ b/tests/test-check-py3-compat.t	Wed Aug 10 04:35:44 2016 +0530
@@ -146,7 +146,7 @@
   mercurial/revlog.py: error importing: <TypeError> getattr(): attribute name must be string (error at util.py:*) (glob)
   mercurial/revset.py: error importing: <TypeError> getattr(): attribute name must be string (error at util.py:*) (glob)
   mercurial/scmutil.py: error importing: <TypeError> getattr(): attribute name must be string (error at util.py:*) (glob)
-  mercurial/scmwindows.py: error importing module: <ImportError> No module named '_winreg' (line *) (glob)
+  mercurial/scmwindows.py: error importing: <TypeError> getattr(): attribute name must be string (error at util.py:*) (glob)
   mercurial/similar.py: error importing: <TypeError> getattr(): attribute name must be string (error at util.py:*) (glob)
   mercurial/simplemerge.py: error importing: <TypeError> getattr(): attribute name must be string (error at util.py:*) (glob)
   mercurial/sshpeer.py: error importing: <TypeError> getattr(): attribute name must be string (error at util.py:*) (glob)
@@ -167,7 +167,7 @@
   mercurial/url.py: error importing: <TypeError> getattr(): attribute name must be string (error at util.py:*) (glob)
   mercurial/verify.py: error importing: <TypeError> attribute name must be string, not 'bytes' (error at mdiff.py:*) (glob)
   mercurial/win32.py: error importing module: <ImportError> No module named 'msvcrt' (line *) (glob)
-  mercurial/windows.py: error importing module: <ImportError> No module named '_winreg' (line *) (glob)
+  mercurial/windows.py: error importing module: <ImportError> No module named 'msvcrt' (line *) (glob)
   mercurial/wireproto.py: error importing module: <TypeError> a bytes-like object is required, not 'str' (line *) (glob)
 
 #endif