ENH: raise a more informative error

[jakevdp]

Raise a more informative error when save is called and no animation writers are available on the system. Previously this situation would lead to an IndexError at the line writer = writers.list()[0]

[pelson]

Thanks @jakevdp. My biggest problem with this change is that I now have to use the writers registry (which I don't use). I think a better approach would be to add a new method on to the writers registry which can return the "first" (in speech marks because we have inconsistent ordering due to use of a dictionary) available writer, or raise an exception (not an IndexError as it used to).

Other than that, I'm in favour of seeing this exception improved.

Thanks,

[jakevdp]

Ah, I didn't think of the possibility of people passing anything but a string to the writer argument... yes, that should be improved.

[jakevdp]

This update should fix the issue.

[pelson]

I'm sorry for being so picky, but ideally we should avoid bare try..except blocks. I think your trying to improve the IndexError which ensues when there are no writers? In which case, would you mind updating this to a try ... except IndexError:.

After that, its good to merge - honest! 😄