apt_key: Fix traceback when key_id format is invalid

Signed-off-by: Philippe Pepiot <phil@philpep.org>
Fix documentation for accept_hostkey
Reset the current directory after running subprocess.Popen
Documentation updates
Be sure to return to the old directory if cwd is set in run_command
Cleaning up some exception blocks in TestModuleUtilsBasic
Updating CHANGELOG/RELEASES in devel for 1.5.3 and older releases
Merge pull request #6477 from angstwad/docs-fix

Documentation updates
Merge pull request #6470 from patrickheeney/doc-git-fix

Fix documentation for accept_hostkey in GIT module
Merge pull request #6468 from philpep/fix_apt_key

apt_key: Fix traceback when key_id format is invalid
Update index.rst
Properly catch import errors in apt

When one accidentally tries to run this module as a user, he gets the error message that python-apt must be installed, no matter what. Because importing apt will trigger an exception as a regular user. Explicitly catching the ImportError will let the exception bubble. The exception clearly says Permission denied somewhere, and the user has a better idea, what he must fix.
Merge pull request #6480 from do3cc/patch-1

Properly catch import errors in apt
Correct check_mode conditional logic

The desired behavior is to _not_ add the ppa signing key when check_mode is
enabled.  This fix corrects the conditional logic to comply with the stated
behavior.
Fixes #6482 Check sysctl file path and catch read exceptions
Merge pull request #6491 from jlaska/apt_repository_signing_fix

[apt_repository] Correct check_mode conditional logic
Unit tests for ansible.utils
Test parse_yaml with leading --- and without
Add test for indented first line in YAML. See #6348
More coverage of ansible.utils