pisi parser is too tolerant of incorrect formatting.

[4fury-c3440d8]

• Create congruent formatting policy for build files.
• Include in pisi's source code pspec.xml and actions.py file formatting checker tool that terminates build with critical error if any file is not indented(spaces or tabs) correctly.

Frequent issues:

• spaces or tabs at the end of strings.
• different characters (spaces or tabs) at the beginning of strings (also, in the same column).
• redundant empty strings.
• incomplete or missing comment at the beginning of file.

[safaariman]

These are actually more about linting. I am not sure if this is a good approach to put code linting into Pisi. This is more like a CI issue. We probably check this with a CI tool at PR stage. We can also prevent people pushing these commits using pre-commit hooks.