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'])
mary</a><a href='/guix/refs/?id=4b8d10ffdb0b2cf9aaf5e774cea6fc56bd9662d1'>refs</a><a class='active' href='/guix/log/.patman'>log</a><a href='/guix/tree/.patman?id=4b8d10ffdb0b2cf9aaf5e774cea6fc56bd9662d1'>tree</a><a href='/guix/commit/.patman?id=4b8d10ffdb0b2cf9aaf5e774cea6fc56bd9662d1'>commit</a><a href='/guix/diff/.patman?id=4b8d10ffdb0b2cf9aaf5e774cea6fc56bd9662d1'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/.patman'>
<input type='hidden' name='id' value='4b8d10ffdb0b2cf9aaf5e774cea6fc56bd9662d1'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=4b8d10ffdb0b2cf9aaf5e774cea6fc56bd9662d1'>root</a>/<a href='/guix/log/.patman?id=4b8d10ffdb0b2cf9aaf5e774cea6fc56bd9662d1'>.patman</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/.patman?id=4b8d10ffdb0b2cf9aaf5e774cea6fc56bd9662d1&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-10-22 16:09:04 -0400'>2023-10-22</span></td><td><a href='/guix/commit/.patman?id=f44fa21c3ec1d9bf1b9da009e1c795942bf654eb'>gnu: patman: Apply patch for new Change-Id setting.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/bootloaders.scm (u-boot) [source]: Apply patch.
* gnu/packages/patches/u-boot-patman-change-id.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.
* .patman (keep_change_id): Use it.

Series-changes: 3
 - New commit
Change-Id: I33c03013f6a260b5f5d80212b7b6ebe8a3f97efa
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2023-05-01 12:39:11 -0400'>2023-05-01</span></td><td><a href='/guix/commit/.patman?id=f21007ce4aceeacf5bbfc7cd45d526073141f194'>.patman: Remove get_maintainer_script option.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is now handled at the level of git via its new '--header-cmd' option,
which produces X-Debbugs-CC headers.

* .patman (get_maintainer_script): Delete option.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2023-02-25 23:10:59 -0500'>2023-02-25</span></td><td><a href='/guix/commit/.patman?id=cb0d8100b288b5b0d130820207db17764b7d2140'>.patman: Ignore bad tags.</a><span class='msg-avail'>...<span class='msg-tooltip'>The feature is not used in Guix, and it produces extraneous warnings.

* .patman (ignore_bad_tags): Set option to True.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-12-28 15:36:33 -0500'>2022-12-28</span></td><td><a href='/guix/commit/.patman?id=fde5af3962c8fafc5d20e5d742cc7aea907f3563'>.patman: New configuration file.</a><span class='msg-avail'>...<span class='msg-tooltip'>* .patman: New file.

Series-to: 60218@debbugs.gnu.org
Series-cc: rekado@elephly.net, othacehe@gnu.org
Series-version: 2
</span></span></td><td>Maxim Cournoyer</td></tr>