Fix hacking.py git checks to propagate errors

Now when N801 or N802 is hit tools/hacking.py will return -1.

Fix bug 1039697

Change-Id: I9f6950a4396ae82861e5de0e4f3ba8b482c4fdf8

tools/hacking.py

@@ -436,7 +436,7 @@ def once_git_check_commit_title():
     """
     #Get title of most recent commit
 
-    subp = subprocess.Popen(['git', 'log', '--pretty=%s', '-1'],
+    subp = subprocess.Popen(['git', 'log', '--no-merges', '--pretty=%s', '-1'],
             stdout=subprocess.PIPE)
     title = subp.communicate()[0]
     if subp.returncode:
@@ -450,20 +450,24 @@ def once_git_check_commit_title():
                     '([Bb]lue[Pp]rint|[Bb][Pp])[\s\#:]*([A-Za-z0-9\\-]+)')
     GIT_REGEX = re.compile(git_keywords)
 
+    error = False
     #NOTE(jogo) if match regex but over 3 words, acceptable title
     if GIT_REGEX.search(title) is not None and len(title.split()) <= 3:
         print ("N801: git commit title ('%s') should provide an accurate "
                "description of the change, not just a reference to a bug "
                "or blueprint" % title.strip())
+        error = True
     if len(title.decode('utf-8')) > 72:
         print ("N802: git commit title ('%s') should be under 50 chars"
                 % title.strip())
+        error = True
+    return error
 
 if __name__ == "__main__":
     #include nova path
     sys.path.append(os.getcwd())
     #Run once tests (not per line)
-    once_git_check_commit_title()
+    once_error = once_git_check_commit_title()
     #NOVA error codes start with an N
     pep8.ERRORCODE_REGEX = re.compile(r'[EWN]\d{3}')
     add_nova()
@@ -473,6 +477,7 @@ if __name__ == "__main__":
     pep8.input_dir = input_dir
     try:
         pep8._main()
+        sys.exit(once_error)
     finally:
         if len(_missingImport) > 0:
             print >> sys.stderr, ("%i imports missing in this test environment"