Utility/example for deleting empty project versions older than <d> days

[OffBy0x01]

• Added new example for deleting empty project versions older than a given number of days
• Made datetime conversion utilities more robust
• Swapped own-implementations for builtin functions where appropriate

Was needing to write something like this anyway, though #173 gave me a little extra motivation :)

Note: I've not been able to fully test this script - please give it a go and let me know if everything looks right.

[skiyooka]

While I am all for deleting code, are these methods that you just recently added e.g. this year? Generally, deleting or changing method signatures are considered as breaking backwards-compatibility in an API.

[OffBy0x01]

None of these were in HubInstance - the only use they had was in demo_client, though I'll update that to use the two new methods.

[skiyooka]

Okay I'm fine with deleting them.

[skiyooka]

I'm getting an exception here: TypeError: can't compare offset-naive and offset-aware datetimes

[OffBy0x01]

A possible solution could be to add something like this to utils:

// from dateutil.tz import tzlocal
def to_local_datetime(date):
    return to_datetime(date).astimezone(tz=tzlocal())   

def get_local_datetime():
    return datetime.now(tz=tzlocal())

Normally I'd avoid creating wrappers for stl functions but in this case I don't think it is obvious how to get a timezone aware datetime given datetime.now() and even datetime.utcnow() are timezone naive. Thoughts?

[skiyooka]

In sage_version_activity_to_csv.py I used: from dateutil.parser import isoparse
Would that work?

[OffBy0x01]

I'll take a look at that tonight

[skiyooka]

You may find https://github.com/blackducksoftware/sage/blob/master/sage_version_activity_to_csv.py interesting as it creates a .csv with one line per project version. The .csv includes all columns I can think of containing decision criteria for deletion. The intended pipeline is to run Sage, then the above script, then filter_activity.py to trim the list to the stuff one just wants to delete.