Add multiline description support, more helpful error messages

[felixvd]

I've encountered some cases that don't tell the user what to fix. This catches the exception and localizes the error.

It also supports multi-line comments.

Example:

def myfunc():
    """Text
    
    :param myparam1: text followed by an empty line (will throw an error)
    
    :param myparam2: more text
        with an extra line (will work fine)
    :param myparam3 which has no closing colon (will throw an error)`
    """
    pass

[a-t-0]

Dear Felix, thank you for your work. I was trying to review your code and thought it would be easier to understand if you could include a test case that demonstrates how your adaptations change the behaviour of pyment. (I noted your example on the support for multiline in the comment with the pull request). Would you perhaps be willing and able to write two of such tests?

• Possibly one to demonstrate how your adaptation yields more helpful error messages.
• And perhaps one that demonstrates the support for multiline descriptions?

Note, I have no affiliations with pyment, however I noticed it has not been updated in almost 1.2 years, so I thought it would be nice to show some interaction to perhaps get the ball rolling (again).