mq: avoid using `__file__` to compare modules

This fixes ~70 tests when using an oxidized executable, bringing the current
failure count down to 92 (with 110 skips) when templates/ is copied next to the
executable.

Differential Revision: https://phab.mercurial-scm.org/D7778

hgext/mq.py

@@ -68,6 +68,7 b' import errno'
 import os
 import re
 import shutil
+import sys
 from mercurial.i18n import _
 from mercurial.node import (
     bin,
@@ -4277,8 +4278,9 b' def extsetup(ui):'
 
     dotable(commands.table)
 
+    thismodule = sys.modules["hgext.mq"]
     for extname, extmodule in extensions.extensions():
-        if extmodule.__file__ != __file__:
+        if extmodule != thismodule:
             dotable(getattr(extmodule, 'cmdtable', {}))