Using warnings.warn() results in TypeError

[dopplershift]

The following code when run in the ipython terminal, qtconsole, and notebook will incorrectly produce a TypeError:

import warnings; warnings.warn('test')

Specifically, running it gives the following trace:

In [1]: import warnings; warnings.warn('test')
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-1-ae902b7aadb6> in <module>()
----> 1 import warnings; warnings.warn('test')

TypeError: expected string or Unicode object, NoneType found

Based on a git bisect, it cropped in with commit 2140420. Specifically, the offending line is 2459 (on master):

save_fname = self.user_ns.get('__file__',None)

If I change None to '', the error goes away and I see the warning. This is important, because it was resulting in tracebacks when numpy would issue a warning. I'm not sure if '' is the proper fix, so I haven't created a PR.

[bfroehle]

Yes, see also #2279. I think directions to fix this can be taken from my post.

[dopplershift]

Hadn't seen that one thanks. Your solution works great for me.

[bfroehle]

Great, I'll close this issue as a duplicate.