This doesn't build for me.

Even with the following patch, it doesn't:

diff --git a/gnu/packages/python-web.scm b/gnu/packages/python-web.scm
index 3d6fd61f10..56496e859f 100644
--- a/gnu/packages/python-web.scm
+++ b/gnu/packages/python-web.scm
@@ -2680,7 +2680,7 @@ List.  Forked from and using the same API as the publicsuffix package.")
     (source
      (origin
        (method url-fetch)
-       (uri (pypi-uri "werkzeug" version))
+       (uri (pypi-uri "Werkzeug" version))
        (sha256
         (base32
          "19kwa1va46jyrhy47fn3a44js1882zrvh70n14mgp0jrh7q1bfd0"))))

Test failure test_windows_get_args_for_reloading