[AIRFLOW-1094] Run unit tests under contrib in Travis

[hgrif]

Dear Airflow maintainers,

Please accept this PR. I understand that it will not be reviewed until I have checked off all the 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-1094

Description

• Here are some details about my PR, including screenshots of any UI changes:

Run unit tests under contrib in Travis

Rename all unit tests under tests/contrib to start with test_* and fix
broken unit tests so that they run for the Python 2 and 3 builds.

General:

• Rename all tests to start with test_*
• Remove imports in tests/*/__init__.py's
• Add missing packages to requirements.txt of CI

BigQueryHook:

• Check for JSON and not json

DataDogSensor:

• Add connection before starting unit tests

DataFlowPythonOperator:

• Use GoogleCloudBucketHelper instead of GoogleCloudStorageHook
• Fix broken assert

ECSOperator:

• Replace sys.maxint by sys.maxsize for Python 3 support
• Allow startedBy to be any argument as CI seems to run it as 'airflow' and not 'Airflow'
• Fix checking of exceptions

SparkSubmitHook:

• Skip tests if Python 3

SqoopHook:

• Remove unneeded OSError (breaking in Python 3)

SSHExecuteOperator:

• Add proper mocks

Zendesk:

• Add under hooks import
• Update import path of BaseHook
• Rewrite pytest unit tests in unittest

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

No extra tests are added, some tests already present are fixed.

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"

[codecov-io]

Codecov Report

Merging #2234 into master will increase coverage by 0.37%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2234      +/-   ##
==========================================
+ Coverage   68.21%   68.58%   +0.37%     
==========================================
  Files         142      142              
  Lines       10957    10957              
==========================================
+ Hits         7474     7515      +41     
+ Misses       3483     3442      -41

Impacted Files	Coverage Δ
airflow/hooks/__init__.py	58.82% <ø> (ø)	⬆️
airflow/hooks/zendesk_hook.py	84.78% <100%> (+84.78%)	⬆️
airflow/models.py	87.22% <0%> (-0.06%)	⬇️
airflow/hooks/base_hook.py	92.15% <0%> (+1.96%)	⬆️
airflow/utils/__init__.py	100% <0%> (+33.33%)	⬆️

---

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 8f9f508...4c42c49. Read the comment docs.

[hgrif]

Hm, only now I see that this PR that was opened earlier.

Anyways, this PR is scoped only to contrib, making merging a bit less dangerous. Some of the improvements in that PR might be more Pythonic than mine, so let me know if I could adapt anything/merge the contrib parts of that PR.

[hgrif]

@bolkedebruin: checked PR 2078 for things to incorporate and limited the scope a bit (less making things look nice).