[SCons] Fix compilation of Python 3 module when PYTHONHOME is set

SConstruct

@@ -672,6 +672,8 @@ print
 # Copy in external environment variables
 if env['env_vars'] == 'all':
     env['ENV'].update(os.environ)
+    if 'PYTHONHOME' in env['ENV']:
+        del env['ENV']['PYTHONHOME']
 elif env['env_vars']:
     for name in env['env_vars'].split(','):
         if name in os.environ:

site_scons/buildutils.py

@@ -591,9 +591,14 @@ def getCommandOutput(cmd, *args):
     Substitute for subprocess.check_output which is only available
     in Python >= 2.7
     """
+    environ = dict(os.environ)
+    if 'PYTHONHOME' in environ:
+        # Can cause problems when trying to run a different Python interpreter
+        del environ['PYTHONHOME']
     proc = subprocess.Popen([cmd] + list(args),
                             stdout=subprocess.PIPE,
-                            stderr=subprocess.PIPE)
+                            stderr=subprocess.PIPE,
+                            env=environ)
     data, err = proc.communicate()
     if proc.returncode:
         raise OSError(err)