setup.py: reload __version__.py after writing it.

write_version loads __version__.py before writing it (see 7eb694a1c1af),
so we have to explicitly reload it to use the correct version.

Problem diagnosed by Christian Ebert.

mercurial/version.py

@@ -1,74 +1,79 b''
 # Copyright (C) 2005, 2006 by Intevation GmbH
 # Author(s):
 # Thomas Arendsen Hein <[e-mail]>
 #
 # This program is free software under the GNU GPL (>=v2)
 # Read the file COPYING coming with the software for details.
 
 """
 Mercurial version
 """
 
 import os
 import os.path
 import re
 import time
 import util
 
 unknown_version = 'unknown'
 remembered_version = False
 
-def get_version():
+def get_version(doreload=False):
     """Return version information if available."""
     try:
-        from mercurial.__version__ import version
+        import mercurial.__version__
+        if doreload:
+            reload(mercurial.__version__)
+        version = mercurial.__version__.version
     except ImportError:
         version = unknown_version
     return version
 
 def write_version(version):
     """Overwrite version file."""
     if version == get_version():
         return
     directory = os.path.dirname(__file__)
     for suffix in ['py', 'pyc', 'pyo']:
         try:
             os.unlink(os.path.join(directory, '__version__.%s' % suffix))
         except OSError:
             pass
     f = open(os.path.join(directory, '__version__.py'), 'w')
     f.write("# This file is auto-generated.\n")
     f.write("version = %r\n" % version)
     f.close()
+    # reload the file we've just written
+    get_version(True)
 
 def remember_version(version=None):
     """Store version information."""
     global remembered_version
     if not version and os.path.isdir(".hg"):
         f = os.popen("hg identify 2> %s" % util.nulldev)  # use real hg installation
         ident = f.read()[:-1]
         if not f.close() and ident:
             ids = ident.split(' ', 1)
             version = ids.pop(0)
             if version[-1] == '+':
                 version = version[:-1]
                 modified = True
             else:
                 modified = False
             if version.isalnum() and ids:
                 for tag in ids[0].split('/'):
                     # is a tag is suitable as a version number?
                     if re.match(r'^(\d+\.)+[\w.-]+$', tag):
                         version = tag
                         break
             if modified:
                 version += time.strftime('+%Y%m%d')
     if version:
         remembered_version = True
         write_version(version)
 
 def forget_version():
     """Remove version information."""
     if remembered_version:
         write_version(unknown_version)