[AIRFLOW-2665] Use shlex to split args and remove shell true

[barrachri]

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Jira

• Jira ticket: https://issues.apache.org/jira/browse/AIRFLOW-2665

Description

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

Currently airflow doesn't support running commands without a bash available, there are not UI changes.

Tests

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

This part was already covered by tests.

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.
  • 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

[barrachri]

I have a small doubt, what is the proper format of a command?:

    def execute_work(self, key, command):
        """
        Executes command received and stores result state in queue.
        :param key: the key to identify the TI
        :type key: Tuple(dag_id, task_id, execution_date)
        :param command: the command to execute
        :type command: string
        """

because looking at the code seems should be a string...but looks like a small lie, because tests were passing alist (this is why I added the isinstance check).

[Fokko]

@bolkedebruin PTAL

[ron819]

Is there update for this?

[ashb]

I don't think this change is needed anymore - since #3740 was merged the command is always a list, so no need to split it.