Update virtualenv requirement from >=21.3.0 to >=21.3.1 (#56)

Updates the requirements on
[virtualenv](https://github.com/pypa/virtualenv) to permit the latest
version.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/pypa/virtualenv/releases">virtualenv's
releases</a>.</em></p>
<blockquote>
<h2>21.3.1</h2>
<!-- raw HTML omitted -->
<h2>What's Changed</h2>
<ul>
<li>👷 ci: retry transient apt failures on Linux by <a
href="https://github.com/gaborbernat"><code>@​gaborbernat</code></a> in
<a
href="https://redirect.github.com/pypa/virtualenv/pull/3139">pypa/virtualenv#3139</a></li>
<li>🐛 fix(seed): bump embedded pip to 26.1.1 by <a
href="https://github.com/gaborbernat"><code>@​gaborbernat</code></a> in
<a
href="https://redirect.github.com/pypa/virtualenv/pull/3138">pypa/virtualenv#3138</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/pypa/virtualenv/compare/21.3.0...21.3.1">https://github.com/pypa/virtualenv/compare/21.3.0...21.3.1</a></p>
</blockquote>
</details>
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a
href="https://github.com/pypa/virtualenv/blob/main/docs/changelog.rst">virtualenv's
changelog</a>.</em></p>
<blockquote>
<h1>Bugfixes - 21.3.1</h1>
<ul>
<li>
<p>Upgrade embedded wheels:</p>
<ul>
<li>pip to <code>26.1.1</code> from <code>26.1</code>
(:issue:<code>3138</code>)</li>
</ul>
</li>
</ul>
<hr />
<p>v21.3.0 (2026-04-27)</p>
<hr />
<h1>Features - 21.3.0</h1>
<ul>
<li>Re-introduce <code>xonsh</code> shell activator
(<code>activate.xsh</code>) previously removed in 20.7.0, and make the
plugin loader
prefer virtualenv's built-in entry points so a third-party package
cannot override them by registering a duplicate
name. (:issue:<code>3003</code>)</li>
</ul>
<h1>Bugfixes - 21.3.0</h1>
<ul>
<li>
<p>Upgrade embedded wheels:</p>
<ul>
<li>pip to <code>26.1</code> (:issue:<code>3132</code>)</li>
</ul>
</li>
</ul>
<hr />
<p>v21.2.4 (2026-04-14)</p>
<hr />
<h1>Bugfixes - 21.2.4</h1>
<ul>
<li>Security hardening: validate each entry of a seed wheel archive
before extracting it so a tampered wheel cannot escape
the app-data image directory via an absolute path or <code>..</code>
traversal. (:issue:<code>3118</code>)</li>
<li>Security hardening: verify the SHA-256 of every bundled seed wheel
when it is loaded so a corrupted or tampered file
on disk fails loud instead of being handed to pip. The hash table is
generated alongside <code>BUNDLE_SUPPORT</code> by
<code>tasks/upgrade_wheels.py</code>. (:issue:<code>3119</code>)</li>
<li>Security hardening: validate the distribution name and version
specifier passed to <code>pip download</code> when acquiring a
seed wheel so extras, pip flags, or shell metacharacters cannot be
smuggled into the subprocess command line.
(:issue:<code>3120</code>)</li>
<li>Security hardening: replace the string-prefix containment check in
<code>virtualenv.util.zipapp</code> with
<code>Path.relative_to</code> so the zipapp extraction helpers refuse
any path that does not resolve under the archive root.
(:issue:<code>3121</code>)</li>
<li>Security hardening: do not silently fall back to an unverified HTTPS
context when the periodic update request to PyPI
fails TLS verification. The returned metadata drives which wheel version
virtualenv considers &quot;up to date&quot;, so
accepting an unverified response lets a network-level attacker suppress
security updates. Set
<code>VIRTUALENV_PERIODIC_UPDATE_INSECURE=1</code> to restore the
previous behavior on hosts with broken trust stores.
(:issue:<code>3122</code>)</li>
</ul>
<hr />
<!-- raw HTML omitted -->
</blockquote>
<p>... (truncated)</p>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/pypa/virtualenv/commit/12ab4957289c1963849bf04a5f35982c928c0a35"><code>12ab495</code></a>
release 21.3.1</li>
<li><a
href="https://github.com/pypa/virtualenv/commit/22eadc4d2738af7e96d744369a7f40df34935c94"><code>22eadc4</code></a>
[pre-commit.ci] pre-commit autoupdate (<a
href="https://redirect.github.com/pypa/virtualenv/issues/3137">#3137</a>)</li>
<li><a
href="https://github.com/pypa/virtualenv/commit/6651dafd919c745adca1e29e31e1d96a1c9e9e52"><code>6651daf</code></a>
🐛 fix(seed): bump embedded pip to 26.1.1 (<a
href="https://redirect.github.com/pypa/virtualenv/issues/3138">#3138</a>)</li>
<li><a
href="https://github.com/pypa/virtualenv/commit/936a36ae63eb8c68123cf9e23824f68aa9ac51b1"><code>936a36a</code></a>
👷 ci: retry transient apt failures on Linux (<a
href="https://redirect.github.com/pypa/virtualenv/issues/3139">#3139</a>)</li>
<li><a
href="https://github.com/pypa/virtualenv/commit/cb5a7d1820871cf26e370c6a954e48326ddd6c57"><code>cb5a7d1</code></a>
[pre-commit.ci] pre-commit autoupdate (<a
href="https://redirect.github.com/pypa/virtualenv/issues/3133">#3133</a>)</li>
<li>See full diff in <a
href="https://github.com/pypa/virtualenv/compare/21.3.0...21.3.1">compare
view</a></li>
</ul>
</details>
<br />


Dependabot will resolve any conflicts with this PR as long as you don't
alter it yourself. You can also trigger a rebase manually by commenting
`@dependabot rebase`.

[//]: # (dependabot-automerge-start)
[//]: # (dependabot-automerge-end)

---

<details>
<summary>Dependabot commands and options</summary>
<br />

You can trigger Dependabot actions by commenting on this PR:
- `@dependabot rebase` will rebase this PR
- `@dependabot recreate` will recreate this PR, overwriting any edits
that have been made to it
- `@dependabot show <dependency name> ignore conditions` will show all
of the ignore conditions of the specified dependency
- `@dependabot ignore this major version` will close this PR and stop
Dependabot creating any more for this major version (unless you reopen
the PR or upgrade to it yourself)
- `@dependabot ignore this minor version` will close this PR and stop
Dependabot creating any more for this minor version (unless you reopen
the PR or upgrade to it yourself)
- `@dependabot ignore this dependency` will close this PR and stop
Dependabot creating any more for this dependency (unless you reopen the
PR or upgrade to it yourself)


</details>

0 files changed, 0 insertions, 0 deletions