-f: optionally read a file with module names to test
-t: bool flag - if set, filter only top-level modules
-e: optionally exclude module names matching the given glob (Unix
shell-style wildcards)
Importing all modules may cause bogus failures in some cases,
eg. when the imported code assumes there is an existing graphical window.
Such behaviour may be by design, hence for automatic processing it's
more convinient to - in some cases - check only for top-level modules
or filter out the troublemakers.
Karolina Surma