Using the latest version from the HP website.
We eventually downloaded the source code from github and changed the file separator.
Problems lines are in src/extensions/iLO REPOSITORY COMMANDS/FwpkgCommand.py
Lines 205 and 263 both use string concatenation and a hardcoded separator of '\\' to create the filename. Changing that constant to '/' fixes the problem on Linux, but would not work on Windows.
Using os.path.join (https://docs.python.org/2/library/os.path.html#os.path.join) would make the code platform independent. Or at least use os.sep (https://docs.python.org/2/library/os.html#os.sep)
As a side comment - distributing this as an executable compiled with pyinstaller adds considerably to the difficulty of making changes. If seuptools was used instead the source code would be much easier to work with.