Automate the gathering of county limit data

[higs4281]

This annual task involves downloading fixed-width files from HUD,
formatting them, combining them and producing a final file that can be
loaded into the owning-a-home API. Included here are a script to
automate that process and a management command to run the script.

Testing

• Run the new manage.py command for 2017:

python manage.py gather_limit_data --year 2017

It will fetch, process and save CSVs, but git status should show no changes, because the data files have already been updated for this year.

If you run the command without a year, it will default to seeking next year's data files, which are not yet available. So you should see the failure message beginning with "Script failed to process all files," and no files should be saved.

python manage.py gather_limit_data

@mthibos If stars align, we should be able to run the bare command next December and grab 2018 values.

[coveralls]

Coverage decreased (-0.1%) to 99.245% when pulling 42463a4 on data-automation2 into 8a92993 on master.

[coveralls]

Coverage decreased (-0.1%) to 99.245% when pulling fb1edda on data-automation2 into 8a92993 on master.

[coveralls]

Coverage increased (+0.003%) to 99.365% when pulling 1fb03ad on data-automation2 into 8a92993 on master.

[coveralls]

Coverage increased (+0.004%) to 99.366% when pulling 34d2541 on data-automation2 into 8a92993 on master.

[chosak]

This might be an edge case, but be careful assigning default values like this. The datetime.date.today().year call happens only once, when the module gets imported, not every time the method gets called with no year argument. It's unlikely to happen, but I have done something similar in the path with

def do_something_based_on_date(date=datetime.date.today()):
    ...

and then spent a bunch of time debugging why my jobs that happened to run around midnight gave strange results. A safer pattern might be to do something like

def get_chums_data(year=None):
    year = year or datetime.date.today().year
    ...

[chosak]

From PEP8:

A bare except: clause will catch SystemExit and KeyboardInterrupt exceptions, making it harder to interrupt a program with Control-C, and can disguise other problems. If you want to catch all exceptions that signal program errors, use except Exception: (bare except is equivalent to except BaseException: ).

[coveralls]

Coverage increased (+0.06%) to 99.424% when pulling 03c9dd9 on data-automation2 into 8a92993 on master.

[coveralls]

Coverage increased (+0.06%) to 99.424% when pulling d12c6e1 on data-automation2 into 8a92993 on master.

[higs4281]

Thank you @chosak for the suggestions.