It looks like pyqt5 is playing dirty and checking the number of args of
functions before calling them. When using hooks.wrap, pyqt5 thinks it
can pass any amount of arguments (because *args) and you get exceptions
like this inside the wrap function, when calling the 'old' function:
>TypeError: onFindDupes() takes 1 positional argument but 2 were given
This commit fixes it by preserving the signature of the wrapped method,
by adding an optional dependency on the "decorator" module.
Making it an optional dependency is probably not the wisest idea but
since this is a small edge case it might be smoother to start like this.
I also added functools.wraps() as a fallback, which won't help much but
is slightly more correct.
See this article for details: https://hynek.me/articles/decorators/
