[GitHub] [airflow] dossett opened a new pull request #5381: AIRFLOW-4740 make default_args end_date permissive

[GitBox <gi...@apache.org>]

dossett opened a new pull request #5381: AIRFLOW-4740 make default_args end_date permissive
URL: https://github.com/apache/airflow/pull/5381
 
 
   Make sure you have checked _all_ steps below.
   
   ### Jira
   
   - [ X] My PR addresses the following [Airflow Jira](https://issues.apache.org/jira/browse/AIRFLOW-4740) 
   
   ### Description
   
   A dag will accept, in its default_args, a `start_date` as simple as `2019-06-01`.  If it detects a string, it converts to a richer type ([code reference|https://github.com/apache/airflow/blob/master/airflow/models/dag.py#L217-L221]). However, it will not accept a similar string for `end_date` instead an exception like this is thrown:
   
   ```
   Traceback (most recent call last):
    File "/airflow/tests/models/test_dag.py", line 210, in test_dag_naive_start_end_dates_strings
    DAG('DAG', default_args={'start_date': '2019-06-01', 'end_date': '2019-06-05'})
    File "/airflow/airflow/models/dag.py", line 244, in __init__
    timezone.convert_to_utc(self.default_args['end_date'])
    File "/airflow/airflow/utils/timezone.py", line 92, in convert_to_utc
    if not is_localized(value):
    File "/airflow/airflow/utils/timezone.py", line 38, in is_localized
    return value.utcoffset() is not None
   AttributeError: 'str' object has no attribute 'utcoffset'
   ```
   
   That's a very confusing user experience.  `end_date` should be as permissive as `start_date`
   
   
   ### Tests
   
   - [X] My PR adds unit tests 
   
   ### Commits
   
   - [X ] My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "[How to write a good git commit message](http://chris.beams.io/posts/git-commit/)":
     1. Subject is separated from body by a blank line
     1. Subject is limited to 50 characters (not including Jira issue reference)
     1. Subject does not end with a period
     1. Subject uses the imperative mood ("add", not "adding")
     1. Body wraps at 72 characters
     1. Body explains "what" and "why", not "how"
   
   ### Code Quality
   
   - [ ] Passes `flake8`
   

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