Just like pip install.

Move the cert config show_value statement to before the
REQUESTS_CA_BUNDLE statement. Removed lines used for testing.

Signed-off-by: NHarsh Vardhan <harsh59v@gmail.com>

Added CA cert information to debug.py
Made the corresponding changes to tests/functional/test_debug.py

Per PEP 599:
https://www.python.org/dev/peps/pep-0599/

- Abstracted out common `get_subdirectory()` code in `Git` and `Mercurial`, adding `get_repo_root_dir()` for the vcs specific code.
- Reverted behaviour of `Git.controls_location()` and `Mercurial.controls_location()` to call the vcs command if the base `VersionControl.controls_location()` doesn't detect the vcs directory.
- Added `log_failed_cmd` argument `VcsSupport.run_command()` to allow vcs commands to be tried without logging errors if they aren't present.
- Corrected indentation.
- Removed `expect_stderr=True` in `test_freeze_mercurial_clone_srcdir` as its not required.

Fix typos.
Co-Authored-By: NChristopher Hunt <chrahunt@gmail.com>

- fixed lint errors.

Added unit test for Mercurial to check for correct behaviour when either the source or setup.py is located in a subdirectory of the repo root.