It's easier to read and contribute to code when it's stylistically consistent. This is a reason why we have PEP 8, the style guide for Python code. It says things like:

Avoid extraneous whitespace in the following situations:...
Immediately before the open parenthesis that starts the argument list of a function call:

Yes: spam(1)
No: spam (1)

Certainly most of the Python code I run across follows that convention. So I got confused when I read Bicho code that sometimes had extraneous whitespace between function name and arguments. Sometimes it did and sometimes it didn't. From a note by one of the maintainers I inferred that Bicho's developers want code to comply with PEP 8.

So I decided to look for those discrepancies, so I could fix them. You can use the pep8 module to find instances of PEP 8 noncompliance, and you can give it arguments to narrow down to just one issue. A command like

$ python pep8.py --select=E211 Bicho/

gave me the list of lines with extraneous whitespace before the open parenthesis. (I've edited out some path-related cruft.) I thought I'd write a regex to fix those lines, but Julia and Leah kindly talked me into seeking out a pre-existing tool first, and I found Pep8ify.

$ pep8ify -f whitespace_before_parameters Bicho/

gave me the proposed fixes as readymade diffs. To make Pep8ify do those fixes:

$ pep8ify -f whitespace_before_parameters Bicho/ -w Bicho/

So now I've filed an issue with a pull request. (I also used Pep8ify to clean up some whitespace inconsistencies around operators like "+" and "=" while I was at it.)

Thanks to Szymon Guz's blog post for pointing me in the right directions.