[AIRFLOW-2407] Resolve Python undefined names

[cclauss]

Make sure you have checked all steps below.

JIRA

• My PR addresses the following Airflow JIRA issues and references them in the PR title. For example, "[AIRFLOW-XXX] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-2407
  • In case you are fixing a typo in the documentation you can prepend your commit with [AIRFLOW-XXX], code changes always need a JIRA issue.

Description

• Here are some details about my PR, including screenshots of any UI changes:
  Combine PRs [AIRFLOW-2407] Declare as global virtualenv_string_args #3293 [AIRFLOW-2407] import logging for line 68 of kerberos_auth.py #3294 [AIRFLOW-2407] import logging for line 76 of aws_hook.py #3296 [AIRFLOW-2407] import logging for line 70 of qubole_sensor.py #3297 [AIRFLOW-2407] Use feature detection for reload() #3298 [AIRFLOW-2407] import AirflowException #3299 into a single pull request as requested at [AIRFLOW-2407] import logging for line 68 of kerberos_auth.py #3294 (comment)

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:
• This PR fixes flake8 tests across the codebase which are currently failing.

Commits

• 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":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Documentation

• In case of new functionality, my PR adds documentation that describes how to use it.
  • When adding new operators/hooks/sensors, the autoclass documentation generation needs to be added.

Code Quality

• Passes git diff upstream/master -u -- "*.py" | flake8 --diff

[codecov-io]

Codecov Report

Merging #3307 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3307   +/-   ##
=======================================
  Coverage   75.88%   75.88%           
=======================================
  Files         197      197           
  Lines       14712    14712           
=======================================
  Hits        11164    11164           
  Misses       3548     3548

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6f68846...9ecb992. Read the comment docs.

[Fokko]

LGTM, thanks @cclauss

[cclauss]

#3298 Should solve one but two other undefined names remain.... flake8 testing of https://github.com/apache/incubator-airflow on Python 3.6.3

$ flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics

./airflow/www/app.py:148:17: F821 undefined name 'reload'
                reload(e)
                ^
./tests/operators/hive_operator.py:178:27: F821 undefined name 'cursor_mock'
                __enter__=cursor_mock,
                          ^
./tests/operators/hive_operator.py:184:27: F821 undefined name 'get_conn_mock'
                __enter__=get_conn_mock,
                          ^
3     F821 undefined name 'reload'
3