fix small bug introduced in last commit, add description to migrate help

migrate/versioning/shell.py

@@ -1,3 +1,6 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+
 """The migrate command-line tool."""
 
 import sys
@@ -58,13 +61,13 @@ def main(argv=None, **kwargs):
     commands = list(api.__all__)
     commands.sort()
 
-    usage = """%%prog COMMAND ...
+    usage = u"""%%prog COMMAND ...
 
     Available commands:
         %s
 
     Enter "%%prog help COMMAND" for information on a particular command.
-    """ % '\n\t'.join(commands)
+    """ % '\n\t'.join([u"%s — %s" % (command.ljust(28), api.command_desc.get(command)) for command in commands])
 
     parser = PassiveOptionParser(usage=usage)
     parser.add_option("-v", "--verbose", action="store_true", dest="verbose")