Bump virtualenv from 20.2.1 to 20.4.2

[dependabot]

Bumps virtualenv from 20.2.1 to 20.4.2.

Changelog

Sourced from virtualenv's changelog.

v20.4.2 (2021-02-01)

Bugfixes - 20.4.2

- Running virtualenv ``--upgrade-embed-wheels`` crashes - by :user:`gaborbernat`. (`[#2058](https://github.com/pypa/virtualenv/issues/2058) <https://github.com/pypa/virtualenv/issues/2058>`_)
v20.4.1 (2021-01-31)
Bugfixes - 20.4.1

• Bump embedded pip and setuptools packages to latest upstream supported (21.0.1 and 52.0.0) - by :user:gaborbernat. ([#2060](https://github.com/pypa/virtualenv/issues/2060) <https://github.com/pypa/virtualenv/issues/2060>_)

v20.4.0 (2021-01-19)

Features - 20.4.0

- On the programmatic API allow passing in the environment variable dictionary to use, defaults to ``os.environ`` if not
  specified - by :user:`gaborbernat`. (`[#2054](https://github.com/pypa/virtualenv/issues/2054) <https://github.com/pypa/virtualenv/issues/2054>`_)
Bugfixes - 20.4.0

• Upgrade embedded setuptools to 51.3.3 from 51.1.2 - by :user:gaborbernat. ([#2055](https://github.com/pypa/virtualenv/issues/2055) <https://github.com/pypa/virtualenv/issues/2055>_)

v20.3.1 (2021-01-13)

Bugfixes - 20.3.1

- Bump embed pip to ``20.3.3``, setuptools to ``51.1.1`` and wheel to ``0.36.2`` - by :user:`gaborbernat`. (`[#2036](https://github.com/pypa/virtualenv/issues/2036) <https://github.com/pypa/virtualenv/issues/2036>`_)
- Allow unfunctioning of pydoc to fail freely so that virtualenvs can be
  activated under Zsh with set -e (since otherwise ``unset -f`` and
  ``unfunction`` exit with 1 if the function does not exist in Zsh) - by
  :user:`d125q`. (`[#2049](https://github.com/pypa/virtualenv/issues/2049) <https://github.com/pypa/virtualenv/issues/2049>`_)
- Drop cached python information if the system executable is no longer present (for example when the executable is a
  shim and the mapped executable is replaced - such is the case with pyenv) - by :user:`gaborbernat`. (`[#2050](https://github.com/pypa/virtualenv/issues/2050) <https://github.com/pypa/virtualenv/issues/2050>`_)
v20.3.0 (2021-01-10)
Features - 20.3.0

• The builtin discovery takes now a --try-first-with argument and is first attempted as valid interpreters. One can use this to force discovery of a given python executable when the discovery order/mechanism raises errors -

... (truncated)

Commits

• 325e95e release 20.4.2
• 531e576 Fix upgrade embeded crashes (#2062)
• d9725b7 Merge pull request #2061 from pypa/release-20.4.1
• 61b2f6f release 20.4.1
• 0e85268 Bump setuptools and pip (#2060)
• 9093686 Merge pull request #2057 from pypa/release-20.4.0
• d47e0a5 release 20.4.0
• a9b0f3b Fix Windows failure (#2056)
• 40aec48 API: Allow passing on the environment variable as an argument (#2054)
• 4c95506 Upgrade embedded setuptools to 51.3.3 from 51.1.2 (#2055)
• Additional commits viewable in compare view

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All committers have signed the CLA.

[LuisAlejandro]

@dependabot rebase

[dependabot]

OK, I won't notify you again about this release, but will get in touch when a new version is available.

If you change your mind, just re-open this PR and I'll resolve any conflicts on it.