Fixed syntax error in run_ptipython script.

Author: jonathanslenders

ptpython/entry_points/run_ptipython.py

@@ -24,7 +24,7 @@ def run():
     a = docopt.docopt(__doc__)
 
     vi_mode = bool(a['--vi'])
-    config_dir = os.path.expanduser(a['--config-dir'] or os.path.join('~', '.ptpython')
+    config_dir = os.path.expanduser(a['--config-dir'] or os.path.join('~', '.ptpython'))
 
     # Create config directory.
     if not os.path.isdir(config_dir) or not os.path.islink(config_dir):