Dash (-) character is invalid in a Python module name

Also invalid in a django app name.

https://lists.launchpad.net/ubuntu-accomplishments-contributors/msg00097.html

```
$ touch test-test.py
$ ipython
Python 2.7.2 (default, Jan 18 2012, 23:14:28) 
Type "copyright", "credits" or "license" for more information.

IPython 0.12 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: import test-test.py
  File "<ipython-input-1-e700c60cfdca>", line 1
    import test-test.py
               ^
SyntaxError: invalid syntax
```