gufw: fix path to python module.

The gufw-pkexec script hardcodes the path to the python module; this
made it error out:

  python3: can't open file '/usr/share/gufw/gufw/gufw.py':
  [Errno 2] No such file or directory

The issue was missed when the package was updated.

Using python entry points should be suggested to upstream, since that's
the standard way of distributing python programs with setuptools.

srcpkgs/gufw/template

@@ -1,7 +1,7 @@
 # Template file for 'gufw'
 pkgname=gufw
 version=21.04.0
-revision=1
+revision=2
 wrksrc="gufw-${version}"
 build_style=python3-module
 hostmakedepends="python3-distutils-extra intltool"
@@ -14,5 +14,7 @@ distfiles="https://github.com/costales/gufw/archive/refs/tags/$version.tar.gz"
 checksum=b57892ec9817ca1520b2fef31cc3ef404b243ef1230bdccfdc6d75ed4e461841
 
 pre_configure() {
-	vsed -i -e "s/python3.5/python$py3_ver/" bin/gufw-pkexec
+	vsed -i -e \
+		"s|/usr/share/gufw/gufw/gufw.py|/usr/lib/python${py3_ver}/site-packages/gufw/gufw.py|" \
+		bin/gufw-pkexec
 }