Fix multi-line strings in Tex and MathTex

[alembcke]

Overview: What does this pull request change?

Fixes Issue #4617. Prior to PR #4515 newlines within a Python string would be stripped by Latex. Since the PR processes the string prior to sending it to Latex, the Python string needs to be stripped of new lines prior to processing (this does not affect Latex new lines, only Python new lines).

Motivation and Explanation: Why and how do your changes improve the library?

To allow for multi-line strings when using Tex and MathTex for code readability.

Links to added or changed documentation pages

N/A

Further Information and Comments

I implemented this by replacing Python new lines with spaces, should I have used self.arg_separator instead of a space? I assumed that users would expect a Python new line to result in a space in the final Latex written to the screen.

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
• If applicable: newly added functions and classes are tested