Since feedparser messes with Python’s internals by assigning
to __code__ it needs to import SGMLParseError too. It also
expects SGMLParseError, which was turned into AssertionError by
https://github.com/python/cpython/commit/e34bbfd61f405eef89e8aa50672b0b25022de320

--- feedparser-6.0.10/feedparser/sgml.py.orig	2023-03-18 09:24:50.976316932 +0100
+++ feedparser-6.0.10/feedparser/sgml.py	2023-03-18 09:26:32.971928811 +0100
@@ -28,6 +28,7 @@
 import re
 
 import sgmllib
+from sgmllib import SGMLParseError
 
 __all__ = [
     'sgmllib',
@@ -41,6 +42,7 @@
     'shorttagopen',
     'starttagopen',
     'endbracket',
+    'SGMLParseError',
 ]
 
 # sgmllib defines a number of module-level regular expressions that are
--- feedparser-6.0.10/feedparser/html.py.orig	2023-03-18 09:32:03.647114745 +0100
+++ feedparser-6.0.10/feedparser/html.py	2023-03-18 09:46:05.021142671 +0100
@@ -349,7 +349,7 @@
 
         try:
             return sgmllib.SGMLParser.parse_declaration(self, i)
-        except sgmllib.SGMLParseError:
+        except AssertionError:
             # Escape the doctype declaration and continue parsing.
             self.handle_data('<')
             return i+1
e'>refs</a><a class='active' href='/guix/log/gnu/packages/mingw.scm?showmsg=1'>log</a><a href='/guix/tree/gnu/packages/mingw.scm?id=f7c4853a6b615f49ed7eb9e7cf9b7d8a1b46f30e'>tree</a><a href='/guix/commit/gnu/packages/mingw.scm?id=f7c4853a6b615f49ed7eb9e7cf9b7d8a1b46f30e'>commit</a><a href='/guix/diff/gnu/packages/mingw.scm?id=f7c4853a6b615f49ed7eb9e7cf9b7d8a1b46f30e'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/mingw.scm'>
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<div class='path'>path: <a href='/guix/log/?id=f7c4853a6b615f49ed7eb9e7cf9b7d8a1b46f30e&amp;showmsg=1'>root</a>/<a href='/guix/log/gnu?id=f7c4853a6b615f49ed7eb9e7cf9b7d8a1b46f30e&amp;showmsg=1'>gnu</a>/<a href='/guix/log/gnu/packages?id=f7c4853a6b615f49ed7eb9e7cf9b7d8a1b46f30e&amp;showmsg=1'>packages</a>/<a href='/guix/log/gnu/packages/mingw.scm?id=f7c4853a6b615f49ed7eb9e7cf9b7d8a1b46f30e&amp;showmsg=1'>mingw.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/mingw.scm?id=f7c4853a6b615f49ed7eb9e7cf9b7d8a1b46f30e'>Collapse</a>)</th><th class='left'>Author</th></tr>
<tr class='logheader'><td><span title='2018-08-09 02:17:25 +0200'>2018-08-09</span></td><td class='logsubject'><a href='/guix/commit/gnu/packages/mingw.scm?id=5c0f11c29cfed59d82ab06d92d2348f0fde30eb8'>gnu: mingw-w64: Update to 5.0.4.</a></td><td>Tobias Geerinckx-Rice</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* gnu/packages/mingw.scm (mingw-w64): Update to 5.0.4.


</td></tr>
<tr class='logheader'><td><span title='2018-03-12 04:57:52 +0100'>2018-03-12</span></td><td class='logsubject'><a href='/guix/commit/gnu/packages/mingw.scm?id=5dacc645b8830d5f65a677bb23a2c93241b165fb'>gnu: mingw-w64: Update to 5.0.3.</a></td><td>Tobias Geerinckx-Rice</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* gnu/packages/mingw.scm (mingw-w64): Update to 5.0.3.


</td></tr>
<tr class='logheader'><td><span title='2018-03-12 04:57:44 +0100'>2018-03-12</span></td><td class='logsubject'><a href='/guix/commit/gnu/packages/mingw.scm?id=8aaba500713df6d0ccd806caff4f24f4c9fcce49'>gnu: mingw-w64: Fix home page and avoid further confusion.</a></td><td>Tobias Geerinckx-Rice</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
MinGW-w64 was forked (in rather dramatic fashion) from the original
MinGW.  The two projects remain distinct and MinGW-w64 seems by far the
actively developed of the two.

* gnu/packages/mingw.scm (mingw-w64)[home-page]: Point to the correct
upstream.  Use HTTPS.
[description]: Expand and briefly note the relationship between the
two projects.  Use @dfn.


</td></tr>
<tr class='logheader'><td><span title='2017-11-08 16:21:53 +0100'>2017-11-08</span></td><td class='logsubject'><a href='/guix/commit/gnu/packages/mingw.scm?id=5a80c15c14760b3989e24c7893bf79afb9f48741'>gnu: Remove "open source" from descriptions.</a></td><td>Ricardo Wurmus</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
All software in Guix is Free Software.

* gnu/packages/aidc.scm (libdmtx)[description]: Remove "open source" string.
* gnu/packages/firmware.scm (seabios)[description]: Likewise.
* gnu/packages/libupnp.scm (libupnp)[description]: Likewise.
* gnu/packages/maths.scm (cubicle)[description]: Likewise.
* gnu/packages/mingw.scm (mingw-w64)[description]: Likewise.
* gnu/packages/game-development.scm (openmw)[description]: Likewise.
[synopsis]: Remove "Free software".


</td></tr>