test-deps.py attempts to check the version of dev-python/markdown used
by dev-util/gi-docgen by importing it. However, on Gentoo there is no
guarantee that the gi-docgen executable and fwupd build scripts use
the same Python interpreter.

--- a/meson.build
+++ b/meson.build
@@ -542,7 +542,7 @@
 fwupd_gir = []
 introspection = get_option('introspection').disable_auto_if(host_machine.system() != 'linux')
 r = run_command([python3, 'docs/test-deps.py'])
-docs_python_deps = get_option('docs').require(r.returncode() == 0, error_message: r.stdout())
+docs_python_deps = get_option('docs')
 gidocgen_dep = dependency('gi-docgen',
   version: '>= 2021.1',
   native: true,