Stackless issue #161: Add Stackless support to patchcheck.py

Now Tools/scripts/patchcheck.py uses Stackless specific git base
branches for Stackless source trees (i.e. "master-slp" instead of
"master")
(cherry picked from commit a4e7d75)

Author: Anselm Kruis

Tools/scripts/patchcheck.py

@@ -10,6 +10,10 @@
 import reindent
 import untabify
 
+try:
+    import stackless
+except ImportError:
+    stackless = None
 
 # Excluded directories which are copies of external libraries:
 # don't check their coding style
@@ -44,6 +48,12 @@ def call_fxn(*args, **kwargs):
     return decorated_fxn
 
 
+def is_stackless():
+    """Check if this is a Stackless Python source"""
+    return (stackless is not None and
+            os.path.exists(os.path.join(SRCDIR, 'Stackless')))
+
+
 def mq_patches_applied():
     """Check if there are any applied MQ patches."""
     cmd = 'hg qapplied'
@@ -87,6 +97,8 @@ def get_base_branch():
         base_branch = "master"
     else:
         base_branch = "{0.major}.{0.minor}".format(version)
+    if is_stackless():
+        base_branch += "-slp"
     this_branch = get_git_branch()
     if this_branch is None or this_branch == base_branch:
         # Not on a git PR branch, so there's no base branch