Inconsistent normalization of config paths can break handling of local packages path

[nrusch]

When overriding "path-like" config values, slashes in paths are not consistently normalized to the current platform, depending on the presence of special patterns (specifically, ~).

When local_packages_path uses different path literals that point to the same path between site and user config files, this will break the value of config.nonlocal_packages_path, and prevent flags like --no-local from working correctly.

Environment

• Windows 10
• Rez 2.114.1
• Rez python version: 3.7.9

To Reproduce

This uses slash differences on Windows to demonstrate the issue, but I can imagine similar issues arising from the use of symlinked directories in config values.

Start with a default rez install.

1. Create a personal ~/.rezconfig.py, and add this to it:

import os
local_packages_path = '{0}/packages'.format(os.path.expanduser('~'))

2. Run this command:

rez-python -c 'import rez.config; print("\n".join(rez.config.config.nonlocal_packages_path))'

Expected behavior
The path to the packages folder in your home directory should not be included in the resulting output.

Actual behavior

• The path to the packages folder in your home directory is included in the resulting output.
• When using rez-env --no-local, packages in your local packages path can still be included in the resolve.

This is because path normalization is currently only applied indirectly based on whether the path contains ~ (smoking gun in rez.utils.formatting.expanduser), and can thus cause inconsistent config behavior.