Seems to be caused by the Python directory being non-decodable; the current working directory does not matter. What is going on is “pydoc” is trying to make a link to a module’s source code, such as

<a href="file:/usr/lib/python3.4/pydoc.py">/usr/lib/python3.4/pydoc.py</a>

For non-decodable paths, the following would work in Firefox:

<a href="file:/home/serhiy/py/cpy%FFthon-3.5/Lib/pydoc.py">/home/serhiy/py/cpy�thon-3.5/Lib/pydoc.py</a>

but since URL percent encoding already uses UTF-8, this scheme isn’t foolproof (e.g. a UTF-8 sequence when the locale is ASCII would be ambiguous). A simpler and more consistent way forward would be an error handler substituting something like this, decoding the surrogate escape code with the “replace” handler, with the HTML link suppressed:

/home/serhiy/py/cpy�thon-3.5/Lib/pydoc.py (invalid filename encoding)