unstructured: Add tests to get all unstructured modules above 90% coverage

[MthwRobinson]

Currently the email.py, pdf.py and email_elements.py files in https://github.com/Unstructured-IO/unstructured have below 90% coverage. The goal of this issue is to add additional tests for those modules to get the coverage above 90%.

Definition of Done

All modules in unstructured have >90% coverage.

References:

• Add tests to get all unstructured modules above 90% coverage unstructured#141

[cragwolfe]

Now following the convention that repo-specific issues are defined in their respective repos. Closing.