Raise a more informative exception when calling civis.io.file_to_dataframe on a file with no url (which likely means the file is expired). I went with a ValueError here but could change it if a different exception would be easier to understand. This error check is pre-empting a ValueError, since the error comes from reading a csv from None.
Raise a more informative exception when calling
civis.io.file_to_dataframeon a file with no url (which likely means the file is expired). I went with aValueErrorhere but could change it if a different exception would be easier to understand. This error check is pre-empting aValueError, since the error comes from reading a csv fromNone.Closes #336.