Update pyinstaller requirement from >=6.0 to >=6.21.0

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---

Updates the requirements on pyinstaller to permit the latest version.

Release notes

Sourced from pyinstaller's releases.

v6.21.0

Please see the v6.21.0 section of the changelog for a list of the changes since v6.20.0.

Changelog

Sourced from pyinstaller's changelog.

6.21.0 (2026-06-13)

Features

* Add support for Python 3.15. (:issue:`9456`)
* Initial support for setting :ref:`alternative splash screen centering modes
  <splash screen centering>` for multi-monitor setups. (:issue:`6271`)
Hooks

* Prevent ``_ios_support`` and ``libobjc.so`` from being collected on non-IOS
  platforms if :mod:`webbrowser` is imported. (:issue:`9436`)
* Update ``scipy`` hook for compatibility with upcoming ``scipy`` v1.18.0.
  (:issue:`9450`)
* Update the ``gi.repository.Adw`` hook to collect translation files
  for ``libadwaita``. (:issue:`9444`)
Documentation

</code></pre>

<ul>

<li>Document known issues with using splash screen in <code>onedir</code> GUI-based

applications. (:issue:<code>9425</code>)</li>

<li>Document the &quot;glowing magenta border&quot; problem in splash screen when

splash screen image contains semi-transparent pixels (for example,

due to feathered edges). (:issue:<code>9425</code>)</li>

</ul>

<h2>6.20.0 (2026-04-22)</h2>

<p>Bugfix</p>

<pre><code>

(Linux) Fix binary dependency analysis in Termux environment; previously,

no binary dependencies would be reported due to mismatched ldd output

pattern. (:issue:9402)
(Linux) Fix compatibility issues with Termux python 3.13, caused by

platform being now reported as &quot;android&quot; instead of &quot;linux&quot; (PEP 738).

(:issue:9398)
(macOS) Fix built-time error when trying to create an .app bundle with

data collected from a directory that contains symlinked elements.

(:issue:9375)
Fix the forkserver spawn mode of multiprocessing under python

3.13.13, 3.14.4, and the upcoming 3.15. (:issue:9423)
Remove warning about non-existing tclX module directory; in some Tcl

&lt;/tr&gt;&lt;/table&gt;

</code></pre>

</blockquote>

<p>... (truncated)</p>

</details>

<details>

<summary>Commits</summary>

<ul>

<li><a href="https://github.com/pyinstaller/pyinstaller/commit/1cda34561015a90b6e1ae31dc89703799adaf13e&quot;&gt;&lt;code&gt;1cda345&lt;/code&gt;&lt;/a> Release v6.21.0. [skip ci]</li>

<li><a href="https://github.com/pyinstaller/pyinstaller/commit/14b6af36cd7284360e7094e66e97ddef76412876&quot;&gt;&lt;code&gt;14b6af3&lt;/code&gt;&lt;/a> tests: use different module in TestModuleGraph::test_find_module</li>

<li><a href="https://github.com/pyinstaller/pyinstaller/commit/6041ae39584fbb0606c1f936e33e656c075859a8&quot;&gt;&lt;code&gt;6041ae3&lt;/code&gt;&lt;/a> tests: modulegraph: skip tests that are incompatible with python 3.15</li>

<li><a href="https://github.com/pyinstaller/pyinstaller/commit/dd3c5601e58fa3b7993486d5bd9f769653f6ee24&quot;&gt;&lt;code&gt;dd3c560&lt;/code&gt;&lt;/a> tests: adjust bytecode sanity-check tests for python 3.15</li>

<li><a href="https://github.com/pyinstaller/pyinstaller/commit/08f4d82600302727dfc210ec38aa9eeebaf7a671&quot;&gt;&lt;code&gt;08f4d82&lt;/code&gt;&lt;/a> modulegraph: adapt _scan_bytecode() for changes in python 3.15</li>

<li><a href="https://github.com/pyinstaller/pyinstaller/commit/13c2e638918528e7b15b7f048aa01d6de9fe9b50&quot;&gt;&lt;code&gt;13c2e63&lt;/code&gt;&lt;/a> modulegraph: improve assert messages in _scan_bytecode()</li>

<li><a href="https://github.com/pyinstaller/pyinstaller/commit/d4fd4f442a214a656e4fc690f86e998d08d46bcb&quot;&gt;&lt;code&gt;d4fd4f4&lt;/code&gt;&lt;/a> depend: bytecode: add support for LOAD_COMMON_CONSTANT</li>

<li><a href="https://github.com/pyinstaller/pyinstaller/commit/5a9f21030ed91f7dc394a24c4e660c742ad6bf07&quot;&gt;&lt;code&gt;5a9f210&lt;/code&gt;&lt;/a> bootstrap: fix issues caused by encodings being frozen in python 3.15</li>

<li><a href="https://github.com/pyinstaller/pyinstaller/commit/8d97d35a2c04162be04a33748318308e09d398a4&quot;&gt;&lt;code&gt;8d97d35&lt;/code&gt;&lt;/a> tests: test_spec_options: explicitly disable argparse colored output</li>

<li><a href="https://github.com/pyinstaller/pyinstaller/commit/10d0772984f885246d002a7963c728c118639225&quot;&gt;&lt;code&gt;10d0772&lt;/code&gt;&lt;/a> tests: use can_import_module('tkinter') with all tkinter/splash tests</li>

<li>Additional commits viewable in <a href="https://github.com/pyinstaller/pyinstaller/compare/v6.0.0...v6.21.0&quot;&gt;compare view</a></li>

</ul>

</details>
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Superseded by #34, which applies this update together with the other pending dependency upgrades on the current main branch and passed the complete Windows, Linux, and macOS CI/packaging matrix.

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