hg: add support for HGUNICODEPEDANTRY environment variable

This lets us easily verify that there are no implicit conversions
between unicodes and bytes in Mercurial's codebase. Based on something
mpm did by hand periodically, but it kept regressing, so just open the
door to running it in a buildbot.

hg

@@ -1,38 +1,43 b''
 #!/usr/bin/env python
 #
 # mercurial - scalable distributed SCM
 #
 # Copyright 2005-2007 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 import os
 import sys
 
+if os.environ.get('HGUNICODEPEDANTRY', False):
+    reload(sys)
+    sys.setdefaultencoding("undefined")
+
+
 libdir = '@LIBDIR@'
 
 if libdir != '@' 'LIBDIR' '@':
     if not os.path.isabs(libdir):
         libdir = os.path.join(os.path.dirname(os.path.realpath(__file__)),
                               libdir)
         libdir = os.path.abspath(libdir)
     sys.path.insert(0, libdir)
 
 # enable importing on demand to reduce startup time
 try:
     from mercurial import demandimport; demandimport.enable()
 except ImportError:
     import sys
     sys.stderr.write("abort: couldn't find mercurial libraries in [%s]\n" %
                      ' '.join(sys.path))
     sys.stderr.write("(check your install and PYTHONPATH)\n")
     sys.exit(-1)
 
 import mercurial.util
 import mercurial.dispatch
 
 for fp in (sys.stdin, sys.stdout, sys.stderr):
     mercurial.util.setbinary(fp)
 
 mercurial.dispatch.run()