Check syntax of mail

[jakobj]

The syntax for using keyword arguments is the mail should be made sure to be consistent, i.e.,

• every opening $ should either be followed by a keyword and a closing $ as in $NAME$
• dollar signs should be escaped by a $, i.e., to write $ in the mail one would need to write $$

If the mail text violates any of these conditions, the program should print an informative error message and exit. Users should be able to override this check by providing a special command line argument.

[pberkes]

Do not fix, I need this for my class

[pberkes]

Do not fix, this year we'll fix it in the ASPP 2018 class!