bug#64803: python-shiboken-6 fails

[Formbi via Bug reports for GNU Guix <bug-guix@gnu.org>]

Hi!

The package python-shiboken-6 fails with this error:

*** Error compiling 'signature_bootstrap.py'...
Sorry: IndentationError: unexpected indent (signature_bootstrap.py, line 64)

The line in question (and the neighboring ones for context) looks like this:

import base64
import importlib
        import importlib.machinery as imachi
import io
import sys
import traceback
import zipfile

I tried adding this to the package definition, but it didn't help:
(add-before 'build 'remove-indent
	    (lambda _
	      (substitute* "sources/shiboken6/libshiboken/embed/signature_bootstrap.py"
			   (("        import importlib.machinery as imachi")
			    "import importlib.machinery as imachi"))))

Someone on IRC suggested to use this, but it didn't work either:
(add-before 'build 'remove-indent
			(lambda _
			  (substitute* "libshiboken/embed/signature_bootstrap.py"
				       (("[ \t]*(import
	       importlib\\.machinery.*)" _ suffix) suffix))))

How should I go about fixing this?

Kind regards