Fix build with Python 3 scons.

Patch taken from Arch Linux:
https://github.com/archlinux/svntogit-packages/blob/packages/serf/trunk/scons-python3.patch

--- serf-1.3.9/SConstruct.orig	2019-07-26 17:49:30.910189251 +0000
+++ serf-1.3.9/SConstruct	2019-07-26 17:49:54.073821735 +0000
@@ -163,9 +163,9 @@
               suffix='.def', src_suffix='.h')
   })
 
-match = re.search('SERF_MAJOR_VERSION ([0-9]+).*'
-                  'SERF_MINOR_VERSION ([0-9]+).*'
-                  'SERF_PATCH_VERSION ([0-9]+)',
+match = re.search(b'SERF_MAJOR_VERSION ([0-9]+).*'
+                  b'SERF_MINOR_VERSION ([0-9]+).*'
+                  b'SERF_PATCH_VERSION ([0-9]+)',
                   env.File('serf.h').get_contents(),
                   re.DOTALL)
 MAJOR, MINOR, PATCH = [int(x) for x in match.groups()]
@@ -183,7 +183,7 @@
 
 unknown = opts.UnknownVariables()
 if unknown:
-  print 'Warning: Used unknown variables:', ', '.join(unknown.keys())
+  print ('Warning: Used unknown variables:', ', '.join(unknown.keys()))
 
 apr = str(env['APR'])
 apu = str(env['APU'])
ix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=99a61391d78f5df6720f14f3596384a61366cef7'>refs</a><a class='active' href='/guix/log/gnu/home/services/media.scm'>log</a><a href='/guix/tree/gnu/home/services/media.scm?id=99a61391d78f5df6720f14f3596384a61366cef7'>tree</a><a href='/guix/commit/gnu/home/services/media.scm?id=99a61391d78f5df6720f14f3596384a61366cef7'>commit</a><a href='/guix/diff/gnu/home/services/media.scm?id=99a61391d78f5df6720f14f3596384a61366cef7'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/home/services/media.scm'>
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<div class='path'>path: <a href='/guix/log/?id=99a61391d78f5df6720f14f3596384a61366cef7'>root</a>/<a href='/guix/log/gnu?id=99a61391d78f5df6720f14f3596384a61366cef7'>gnu</a>/<a href='/guix/log/gnu/home?id=99a61391d78f5df6720f14f3596384a61366cef7'>home</a>/<a href='/guix/log/gnu/home/services?id=99a61391d78f5df6720f14f3596384a61366cef7'>services</a>/<a href='/guix/log/gnu/home/services/media.scm?id=99a61391d78f5df6720f14f3596384a61366cef7'>media.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/home/services/media.scm?id=99a61391d78f5df6720f14f3596384a61366cef7&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-03-16 23:03:17 +0100'>2023-03-16</span></td><td><a href='/guix/commit/gnu/home/services/media.scm?id=8f219e658d8d2d89a2d6ec10729099130791a3a2'>home: services: kodi, znc, ssh-agent: Use 'match-record'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/home/services/media.scm (home-kodi-services): Use 'match-record'
instead of 'match'.
* gnu/home/services/messaging.scm (home-znc-services): Likewise.
* gnu/home/services/ssh.scm (home-ssh-agent-services): Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2023-03-16 17:23:51 +0100'>2023-03-16</span></td><td><a href='/guix/commit/gnu/home/services/media.scm?id=6afd1fd6bccf3093c6e7b29ed816ee0d5a10c537'>home: services: kodi: Remove host-side use of (shepherd support).</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a followup to 70056b1b2beebbc9f8ea2c34eacc57f379368ab3, which
inadvertently pulled in (shepherd support) on the host side.

* gnu/home/services/media.scm (home-kodi-services): Change 'command' and
'logfile' to gexps.  Add 'modules' field to 'shepherd-service'.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2023-03-16 14:33:16 +0100'>2023-03-16</span></td><td><a href='/guix/commit/gnu/home/services/media.scm?id=70056b1b2beebbc9f8ea2c34eacc57f379368ab3'>gnu: home: services: Add home-kodi-service-type.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/home/services/media.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* po/guix/POTFILES.in: Likewise.
* doc/guix.texi (Media Home Services): Document it in new subsection.
</span></span></td><td>Jan (janneke) Nieuwenhuizen</td></tr>