In certain environments such as in a FIPS enabled system,
certain algorithms such as md5 may be unavailable. Due
to the importing of such a module on a system where it
is unavailable, urllib will crash and is unusable.

This change makes the code more resilient by deferring the
usage of the hash function module unless they are required.
If the hash function is unavailable but required, an SSLError
is raised indicating the same. If the hash function is unavailable
but not required, urllib functions instead of crashing.

Co-authored-by: Thomas Grainger <tagrain@gmail.com>

70b851b

)

As per the following warnings, the v1.x branches of urllib3 will stop
building with up-to-date setuptools by 2024-09-26 if not addressed:

    /usr/lib/python3.12/site-packages/setuptools/dist.py:476: SetuptoolsDeprecationWarning: Invalid dash-separated options
    !!

            ********************************************************************************
            Usage of dash-separated 'provides-extra' will not be supported in future
            versions. Please use the underscore name 'provides_extra' instead.

            By 2024-Sep-26, you need to update your project and remove deprecated calls
            or your builds will no longer be supported.

            See https://setuptools.pypa.io/en/latest/userguide/declarative_config.html for details.
            ********************************************************************************

    !!
      opt = self.warn_dash_deprecation(opt, section)
    /usr/lib/python3.12/site-packages/setuptools/dist.py:476: SetuptoolsDeprecationWarning: Invalid dash-separated options
    !!

            ********************************************************************************
            Usage of dash-separated 'requires-dist' will not be supported in future
            versions. Please use the underscore name 'requires_dist' instead.

            By 2024-Sep-26, you need to update your project and remove deprecated calls
            or your builds will no longer be supported.

            See https://setuptools.pypa.io/en/latest/userguide/declarative_config.html for details.
            ********************************************************************************