Bump virtualenv from 21.7.14 to 21.7.16 (aio-libs#13788)

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 21.7.14 to
21.7.16.
<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>21.7.16</h2>
<!-- raw HTML omitted -->
<h2>What's Changed</h2>
<ul>
<li>📝 docs(security): add an incident response plan by <a
href="https://github.com/gaborbernat"><code>@​gaborbernat</code></a> in
<a
href="https://redirect.github.com/pypa/virtualenv/pull/3262">pypa/virtualenv#3262</a></li>
<li>📝 docs(security): document both reporting lanes and scope by <a
href="https://github.com/gaborbernat"><code>@​gaborbernat</code></a> in
<a
href="https://redirect.github.com/pypa/virtualenv/pull/3261">pypa/virtualenv#3261</a></li>
<li>🐛 fix(activation): escape csh prompt expansion characters by <a
href="https://github.com/gaborbernat"><code>@​gaborbernat</code></a> in
<a
href="https://redirect.github.com/pypa/virtualenv/pull/3263">pypa/virtualenv#3263</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/pypa/virtualenv/compare/21.7.15...21.7.16">https://github.com/pypa/virtualenv/compare/21.7.15...21.7.16</a></p>
<h2>21.7.15</h2>
<!-- raw HTML omitted -->
<h2>What's Changed</h2>
<ul>
<li>🐛 fix(activation): restore empty saved values on deactivate by <a
href="https://github.com/gaborbernat"><code>@​gaborbernat</code></a> in
<a
href="https://redirect.github.com/pypa/virtualenv/pull/3259">pypa/virtualenv#3259</a></li>
<li>🐛 fix(activation): make csh deactivate work without test by <a
href="https://github.com/gaborbernat"><code>@​gaborbernat</code></a> in
<a
href="https://redirect.github.com/pypa/virtualenv/pull/3260">pypa/virtualenv#3260</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/pypa/virtualenv/compare/21.7.14...21.7.15">https://github.com/pypa/virtualenv/compare/21.7.14...21.7.15</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 - 21.7.16</h1>
<ul>
<li>Fix <code>activate.csh</code> rendering the venv's prompt text wrong
when it contains <code>!</code> (csh and tcsh both expand it) or
<code>%</code> (tcsh only, since plain csh has no <code>%</code> prompt
escape at all). (:issue:<code>3263</code>)</li>
</ul>
<hr />
<p>v21.7.15 (2026-09-18)</p>
<hr />
<h1>Bugfixes - 21.7.15</h1>
<ul>
<li>Restore an empty <code>PATH</code> on <code>deactivate</code> in the
bash and fish activators, and stop bash leaving the prompt in
<code>PS1</code> when it was unset before activation.
(:issue:<code>3259</code>)</li>
<li>Fix <code>activate.csh</code> failing to restore <code>PATH</code>
and other saved variables on <code>deactivate</code> when
<code>PATH</code> was already
empty. (:issue:<code>3260</code>)</li>
</ul>
<hr />
<p>v21.7.14 (2026-09-18)</p>
<hr />
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/pypa/virtualenv/commit/4c946c2555260b87d94b2f8ede45215e2f75e70b"><code>4c946c2</code></a>
release 21.7.16</li>
<li><a
href="https://github.com/pypa/virtualenv/commit/630ae100ca873e619ff7dad2174ea25dc3b9454e"><code>630ae10</code></a>
🐛 fix(activation): escape csh prompt expansion characters (<a
href="https://redirect.github.com/pypa/virtualenv/issues/3263">#3263</a>)</li>
<li><a
href="https://github.com/pypa/virtualenv/commit/496e8c903d695051f8a4e27de481e25c9c42d865"><code>496e8c9</code></a>
📝 docs(security): document both reporting lanes and scope (<a
href="https://redirect.github.com/pypa/virtualenv/issues/3261">#3261</a>)</li>
<li><a
href="https://github.com/pypa/virtualenv/commit/85606520d3f56bf6eaefd1233f177119dd8dbb00"><code>8560652</code></a>
📝 docs(security): add an incident response plan (<a
href="https://redirect.github.com/pypa/virtualenv/issues/3262">#3262</a>)</li>
<li><a
href="https://github.com/pypa/virtualenv/commit/502d383b4e1af50fb66486b2666eac31ff5c4537"><code>502d383</code></a>
release 21.7.15</li>
<li><a
href="https://github.com/pypa/virtualenv/commit/fc2f35f51d563c495564f4709ec1a22f0c686352"><code>fc2f35f</code></a>
🐛 fix(activation): make csh deactivate work without test (<a
href="https://redirect.github.com/pypa/virtualenv/issues/3260">#3260</a>)</li>
<li><a
href="https://github.com/pypa/virtualenv/commit/ee55cc271542fdbfd2d38151196ca18019282736"><code>ee55cc2</code></a>
🐛 fix(activation): restore empty saved values on deactivate (<a
href="https://redirect.github.com/pypa/virtualenv/issues/3259">#3259</a>)</li>
<li>See full diff in <a
href="https://github.com/pypa/virtualenv/compare/21.7.14...21.7.16">compare
view</a></li>
</ul>
</details>
<br />


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requirements/constraints.txt

@@ -336,7 +336,7 @@ uvloop==0.22.1 ; platform_system != "Windows"
     #   -r requirements/lint.in
 valkey==6.1.1
     # via -r requirements/lint.in
-virtualenv==21.7.14
+virtualenv==21.7.16
     # via pre-commit
 wheel==0.48.0
     # via pip-tools

requirements/dev.txt

@@ -326,7 +326,7 @@ uvloop==0.22.1 ; platform_system != "Windows" and implementation_name == "cpytho
     #   -r requirements/lint.in
 valkey==6.1.1
     # via -r requirements/lint.in
-virtualenv==21.7.14
+virtualenv==21.7.16
     # via pre-commit
 wheel==0.48.0
     # via pip-tools

requirements/lint.txt

@@ -166,7 +166,7 @@ uvloop==0.22.1 ; platform_system != "Windows"
     # via -r requirements/lint.in
 valkey==6.1.1
     # via -r requirements/lint.in
-virtualenv==21.7.14
+virtualenv==21.7.16
     # via pre-commit
 yarl==1.25.1
     # via aiohttp