gettz on Python 3 fails with TypeError when passed bytes

[labrys]

Given the following code on Python 3.7:

import dateutil.tz
dateutil.tz.gettz(b'America/New_York')

A TypeError is raised:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "lib/python3.7/site-packages/dateutil/tz/tz.py", line 1551, in __call__
    rv = self.nocache(name=name)
  File "lib/python3.7/site-packages/dateutil/tz/tz.py", line 1612, in nocache
    if name.startswith(":"):
TypeError: startswith first arg must be bytes or a tuple of bytes, not str

[labrys]

To be clear, a TypeError being raised for bytes isn't the problem since the docs say "Retrieve a time zone object from a string representation".

The problem is more that the raised error is unhelpful and should consider raising the TypeError with a more helpful message such as TypeError: gettz arg should be str, not bytes

[pganssle]

@labrys Thanks for the report, sorry for the delay in responding. I agree with the proposed solution.

For anyone who is interested in implementing this - please benchmark your solution for the non-failing condition. I am not sure having a nice error message for this is worth a significant performance hit when someone is properly passing str.

[labrys]

@pganssle A try-except-raise should have little to no effect for valid values, but definitely no harm in profiling it :)