key_without_language() reimplemented with regexp

[atilante]

Description

What?

This pull request contains several related modifications to A+ RST Tools issue #134. https://github.com/apluslms/a-plus-rst-tools/issues/134

1. In lib/toc_languages.py, functions key_without_language() and join_keys() were refactored into methods in the class IndexJoiner. This is more consistent, as there are other "join"-named methods in IndexJoiner.

2. Method key_without_language() in lib/toclanguages.py had a bug: the function could only strip language ids of form "id" and "id-", not "_id" or "id". The bug was discovered with course the CS-A1141 Data Structures and Algorithms Y. The function is now reimplemented with a more flexible regular expression.

3. Method join_keys in lib/toc_languages.py now prints a warning message into log. The message describes the location of mismatching keys in the documentation tree, and mismatching keys with their language identifiers. Example:

   Mismatching keys at modules.1.2.3: Language: en Key: sorting_en_something Language: fi Key: sorting_fi_different

This should help the course material author locate the error. Moreover, as the method now logs an error message instead of raising a SphinxError, the compilation process can show log messages of all mismatching keys at one compilation run, thus increasing productivity.

4. Unit test file tests/test_toc_languages.py tests the aforementioned modified functions. The unit tests allow the A-plus RST tools developer to: (i) easily test the functions of the software without needing to run a Sphinx compilation of a test material, which can take minutes; (ii) document how the functions should respond to certain inputs.

Why?

A+ RST Tools could not produce a helpful error message when there was something inconsistent with keys on multilingual courses.

How?

Described above.

Fixes #134

Testing

Python unit tests are introduced to A+ RST Tools in this pull request. There is the new directory "tests".

What type of test did you run?

• [ ] Accessibility test using the WAVE extension.
• [ ] Django unit tests.
• [ ] Selenium tests.
• [x] Other test. (Add a description below)
• [ ] Manual testing.

[ADD A DESCRIPTION ABOUT WHAT YOU TESTED MANUALLY]

Did you test the changes in

• [ ] Chrome
• [ ] Firefox
• [x] This pull request cannot be tested in the browser.

Think of what is affected by these changes and could become broken

Translation

• [x] Did you modify or add new strings in the user interface? Original error message:

  Corresponding RST file names must match in multilingual courses:
  fi_something
  en_different

  Modified error message:

  Mismatching keys at modules.1.2.3:
  Language: en Key: sorting_en_something
  Language: fi Key: sorting_fi_different

Programming style

• [X] Did you follow our style guides?

Have you updated the README or other relevant documentation?

• [ ] documents inside the doc directory.
• [ ] README.md.
• [ ] Aplus Manual.
• [x] Other documentation: tests/README.md

Is it Done?

• [ ] Reviewer has finished the code review
• [ ] After the review, the developer has made changes accordingly
• [ ] Customer/Teacher has accepted the implementation of the feature

Clean up your git commit history before submitting the pull request!