setup: set whole env for running hg even if .hg doesn't exist (issue3073)

The issue was partially fixed by b357a972d6cd, but there were missing
variables to run build_hgextindex.

setup.py

@@ -133,14 +133,13 b' def runhg(cmd, env):'
 
 version = ''
 
-env = {'HGRCPATH': '', 'LANGUAGE': 'C'}
-
-if os.path.isdir('.hg'):
     # Execute hg out of this directory with a custom environment which
     # includes the pure Python modules in mercurial/pure. We also take
     # care to not use any hgrc files and do no localization.
     pypath = ['mercurial', os.path.join('mercurial', 'pure')]
-    env['PYTHONPATH'] = os.pathsep.join(pypath)
+env = {'PYTHONPATH': os.pathsep.join(pypath),
+       'HGRCPATH': '',
+       'LANGUAGE': 'C'}
     if 'LD_LIBRARY_PATH' in os.environ:
         env['LD_LIBRARY_PATH'] = os.environ['LD_LIBRARY_PATH']
     if 'SystemRoot' in os.environ:
@@ -148,6 +147,8 b" if os.path.isdir('.hg'):"
         # under Windows. Otherwise, the subprocess will fail with
         # error 0xc0150004. See: http://bugs.python.org/issue3440
         env['SystemRoot'] = os.environ['SystemRoot']
+
+if os.path.isdir('.hg'):
     cmd = [sys.executable, 'hg', 'id', '-i', '-t']
     l = runhg(cmd, env).split()
     while len(l) > 1 and l[-1][0].isalpha(): # remove non-numbered tags