python3: cli: add workaround for required subcommand

http://bugs.python.org/issue9253#msg186387

Fixes #239

Signed-off-by: Ruslan Kuprieiev <[email protected]>

dvc/cli.py

@@ -1,5 +1,6 @@
 from __future__ import print_function
 
+import sys
 import argparse
 from multiprocessing import cpu_count
 
@@ -55,6 +56,11 @@ def parse_args(argv=None):
                         dest='cmd',
                         help='Use dvc CMD --help for command-specific help')
 
+    # NOTE: Workaround for bug in Python 3
+    if sys.version_info[0] == 3:
+        subparsers.required = True
+        subparsers.dest = 'cmd'
+
     # Init
     init_parser = subparsers.add_parser(
                         'init',