removing extra blank lines

repo2docker/app.py

@@ -351,7 +351,6 @@ class Repo2Docker(Application):
             help='Print the repo2docker version and exit.'
         )
 
-
         return argparser
 
     def json_excepthook(self, etype, evalue, traceback):
@@ -363,7 +362,6 @@ class Repo2Docker(Application):
                        exc_info=(etype, evalue, traceback),
                        extra=dict(phase='failed'))
 
-
     def initialize(self, argv=None):
         """Init repo2docker configuration before start"""
         if argv is None: