Adjust the log_path DeprecationWarning's stack level

[edmorley]

Meta -

OS: Windows 10
Selenium Version:
Browser: Firefox
Browser Version: 63.0a1

Expected Behavior -

That the DeprecationWarning added in #5979 sets an appropriate stacklevel, so that the warning references the offending caller, and not the file + line number of where the logger.warn() is called.

Actual Behavior -

stacklevel not used, so the stack trace doesn't point at the offending caller:

        if log_path:
>           warnings.warn('use service_log_path instead of log_path', DeprecationWarning)
E           DeprecationWarning: use service_log_path instead of log_path
../../../venv/lib/python2.7/site-packages/selenium/webdriver/firefox/webdriver.py:104: DeprecationWarning

Steps to reproduce -

Update a project using pytest-selenium 1.13 from selenium 3.13.0 to 3.14.0 with DeprecationWarnings as errors. eg:
mozilla/treeherder#3872
https://travis-ci.org/mozilla/treeherder/jobs/411325051#L947

[lmtierney]

Currently none of our DeprecationWarning warnings have a stacklevel different than default. I'm not against changing this, but if we do it for service_log_path we should probably do it for all of them.

Thoughts @AutomatedTester ?

[AutomatedTester]

Sounds good to me, as more people start hiding Selenium in their packages it's going be required more.

[lmtierney]

Added stacklevel=2 to all DeprecationWarning via 18681a6

[edmorley]

Many thanks :-)