add "--failfast" (stop on first failure) mode to test runner (if supported by...

add "--failfast" (stop on first failure) mode to test runner (if supported by Python's unittest module)

runtests.py

@@ -1837,6 +1837,9 @@ def main():
     parser.add_option("--exit-ok", dest="exit_ok", default=False,
                       action="store_true",
                       help="exit without error code even on test failures")
+    parser.add_option("--failfast", dest="failfast", default=False,
+                      action="store_true",
+                      help="stop on first failure or error")
     parser.add_option("--root-dir", dest="root_dir", default=os.path.join(DISTDIR, 'tests'),
                       help="working directory")
     parser.add_option("--work-dir", dest="work_dir", default=os.path.join(os.getcwd(), 'TEST_TMP'),
@@ -2137,8 +2140,15 @@ def runtests(options, cmd_args, coverage=None):
             except OSError: pass  # concurrency issue?
         test_runner = XMLTestRunner(output=xml_output_dir,
                                     verbose=options.verbosity > 0)
+        if options.failfast:
+            sys.stderr.write("--failfast not supported with XML runner")
     else:
-        test_runner = unittest.TextTestRunner(verbosity=options.verbosity)
+        text_runner_options = {}
+        if options.failfast and sys.version_info < (2, 7):
+            sys.stderr.write("--failfast not supported with Python < 2.7")
+        else:
+            text_runner_options['failfast'] = True
+        test_runner = unittest.TextTestRunner(verbosity=options.verbosity, **text_runner_options)
 
     if options.pyximport_py:
         from pyximport import pyximport