[AIRFLOW-4837] Fix pylint errors regarding ungrouped imports

[mik-laj]

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-4837] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-4837
  • In case you are fixing a typo in the documentation you can prepend your commit with [AIRFLOW-4837], code changes always need a Jira issue.
  • In case you are proposing a fundamental code change, you need to create an Airflow Improvement Proposal (AIP).
  • In case you are adding a dependency, check if the license complies with the ASF 3rd Party License Policy.

Description

This change fixes the following errors:

tests/operators/test_mssql_to_hive.py:27:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/operators/test_hive_stats_operator.py:23:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/operators/test_s3_file_transform_operator.py:30:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/core.py:24:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/core.py:40:0: C0412: Imports from package tempfile are not grouped (ungrouped-imports)
tests/utils/test_dag_processing.py:28:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/utils/test_operator_helpers.py:23:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/models/test_dag.py:31:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/models/test_connection.py:24:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/models/test_taskinstance.py:27:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/models/test_dagbag.py:28:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/cli/test_cli.py:26:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/contrib/sensors/test_qubole_sensor.py:24:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/contrib/sensors/test_ftp_sensor.py:23:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/contrib/sensors/test_emr_step_sensor.py:22:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/contrib/sensors/test_emr_job_flow_sensor.py:23:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/contrib/operators/test_emr_create_job_flow_operator.py:24:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/contrib/operators/test_emr_add_steps_operator.py:23:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/contrib/operators/test_gcp_transfer_operator_system_helper.py:29:0: C0412: Imports from package googleapiclient are not grouped (ungrouped-imports)
tests/contrib/operators/test_dataproc_operator.py:47:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/contrib/operators/test_hive_to_dynamodb_operator.py:25:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/contrib/operators/test_gcp_sql_operatorquery_system.py:23:0: C0412: Imports from package os are not grouped (ungrouped-imports)
tests/contrib/hooks/test_azure_container_instance_hook.py:23:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/contrib/hooks/test_gcp_api_base_hook.py:34:0: C0412: Imports from package google are not grouped (ungrouped-imports)
tests/contrib/hooks/test_jdbc_hook.py:24:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/contrib/hooks/test_bigquery_hook.py:25:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/contrib/hooks/test_spark_sql_hook.py:25:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/www/test_utils.py:24:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/www/test_security.py:22:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/www/test_views.py:31:0: C0412: Imports from package urllib are not grouped (ungrouped-imports)
tests/www/test_views.py:33:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/www/api/experimental/test_kerberos_endpoints.py:24:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/ti_deps/deps/test_task_concurrency.py:22:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/ti_deps/deps/test_valid_state_dep.py:22:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/ti_deps/deps/test_prev_dagrun_dep.py:22:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/ti_deps/deps/test_not_in_retry_period_dep.py:23:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/ti_deps/deps/test_ready_to_reschedule_dep.py:22:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/ti_deps/deps/test_not_running_dep.py:22:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/executors/test_celery_executor.py:25:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/executors/test_celery_executor.py:40:0: C0412: Imports from package celery are not grouped (ungrouped-imports)
tests/hooks/test_hive_hook.py:29:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/hooks/test_s3_hook.py:23:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)
tests/task/task_runner/test_standard_task_runner.py:23:0: C0412: Imports from package unittest are not grouped (ungrouped-imports)

Tests

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

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 (not including Jira issue reference)
  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.
  • All the public functions and the classes in the PR contain docstrings that explain what it does
  • If you implement backwards incompatible changes, please leave a note in the Updating.md so we can assign it to a appropriate release

Code Quality

• Passes flake8

[codecov-io]

Codecov Report

Merging #5464 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5464      +/-   ##
==========================================
- Coverage   79.13%   79.13%   -0.01%     
==========================================
  Files         488      488              
  Lines       30608    30608              
==========================================
- Hits        24223    24222       -1     
- Misses       6385     6386       +1

Impacted Files	Coverage Δ
airflow/models/taskinstance.py	93.02% <0%> (-0.17%)	⬇️

---

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 d5a5b9d...696b590. Read the comment docs.