py3: move xrange alias next to import lines

Builtin functions should be available in compatibility code.

mercurial/pycompat.py

@@ -29,6 +29,12 b' else:'
     import urllib.parse as urlparse
     import xmlrpc.client as xmlrpclib
 
+try:
+    xrange
+except NameError:
+    import builtins
+    builtins.xrange = range
+
 stringio = io.StringIO
 empty = _queue.Empty
 queue = _queue.Queue
@@ -143,9 +149,3 b' except ImportError:'
         "SimpleHTTPRequestHandler",
         "CGIHTTPRequestHandler",
     ))
-
-try:
-    xrange
-except NameError:
-    import builtins
-    builtins.xrange = range