v1.20.2

• Dependencies that depend on the version of Python being used are now specified using the Declaring platform specific dependencies syntax in setuptools <https://setuptools.readthedocs.io/en/latest/setuptools.html#declaring-platform-specific-dependencies>__. This means that more recent versions of dependencies are likely to be installed on Python 3.6 and later, and unnecessary backport libraries won't be installed on more recent Python versions.