Add check_rubocop

Uses rubocop to check syntax / style of ruby files.

pre_commit_hooks/check_rubocop.py

@@ -0,0 +1,27 @@
+from __future__ import print_function
+
+import argparse
+import subprocess
+import sys
+
+
+def check_rubocop(argv=None):
+    parser = argparse.ArgumentParser()
+    parser.add_argument('filenames', nargs='*', help='filenames to check.')
+    args = parser.parse_args(argv)
+
+    retval = 0
+
+    command = ["rubocop"] + args.filenames
+
+    try:
+        retval = subprocess.check_call(command, shell=False)
+    except subprocess.CalledProcessError as err:
+        print('{0}: rubocop failed ({1})'.format(args.filenames, err))
+        retval = 1
+
+    return retval
+
+
+if __name__ == '__main__':
+    sys.exit(check_rubocop())