fix: issue #2 added tests to get branch coverage 100%

[Dajamante]

Describe your change:

Functions:
data_structures/queue/priority_queue_using_list.py and queue_on_pseudo_stack.py were fixed with updating path to allow doctest to run exceptions. Making tests for the two exceptions not covered. The coverage is now 100% according to the python coverage tool.

datastructure/binary_tree/binary_search_tree.py tests were standardized. Current coverage 65%

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.

[jacobmimms]

LGTM