Fix incorrect usage of lstrip bug in fileutils tests

[theartful]

I'm using Arch linux (typical starting statement of an arch user lol), and one of the packages I use depend on boltons (https://aur.archlinux.org/packages/python-boltons). I faced an issue with tests failing causing me to do some manual intervention.

On my machine, I have

BOLTONS_PATH = "/home/theartful/.cache/yay/python-boltons/src/boltons/boltons"

The test checks that "fileutils.py" can be found using iter_find_files, and indeed it is part of iter_find_files(BOLTONS_PATH, patterns=['*.py']) as:

p = "/home/theartful/.cache/yay/python-boltons/src/boltons/boltons/fileutils.py"

The bug here is that "lstrip" doesn't remove the prefix, but instead removes all characters from the left that is part of the string. For example:

>>> BOLTONS_PATH = "/home/theartful/.cache/yay/python-boltons/src/boltons/boltons"
>>> p = "/home/theartful/.cache/yay/python-boltons/src/boltons/boltons/fileutils.py"
>>> p.lstrip(BOLTONS_PATH)
 ileutils.py

[mahmoud]

Great catch, sincere thanks from a reformed Gentoo/Arch user. This is a classic bug, but we have to do a bit more to make the tests pass on older Pythons and Windows.

Here's a removeprefix that you can just drop in the file and use, or add to strutils if you're so inclined:

def removeprefix(text: str, prefix: str) -> str:
    if text.startswith(prefix):
        return text[len(prefix):]
    return text

As for Windows, the file path separator is throwing off tests, so we still need to strip that out with .lstrip(os.path.sep)

Looking forward to merging this, thanks again!

[theartful]

I added removeprefix to strutils.py. I forgot all about windows and their usage of backslashes instead of forward slashes.

[mahmoud]

Looks great! Thanks so much again!