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'])
guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=71e1d0a4373f6cc5cd99e1400fb87d64d97c370f'>refs</a><a class='active' href='/guix/log/gnu/packages/bootloaders.scm'>log</a><a href='/guix/tree/gnu/packages/bootloaders.scm?id=71e1d0a4373f6cc5cd99e1400fb87d64d97c370f'>tree</a><a href='/guix/commit/gnu/packages/bootloaders.scm?id=71e1d0a4373f6cc5cd99e1400fb87d64d97c370f'>commit</a><a href='/guix/diff/gnu/packages/bootloaders.scm?id=71e1d0a4373f6cc5cd99e1400fb87d64d97c370f'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/bootloaders.scm'>
<input type='hidden' name='id' value='71e1d0a4373f6cc5cd99e1400fb87d64d97c370f'/><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=71e1d0a4373f6cc5cd99e1400fb87d64d97c370f'>root</a>/<a href='/guix/log/gnu?id=71e1d0a4373f6cc5cd99e1400fb87d64d97c370f'>gnu</a>/<a href='/guix/log/gnu/packages?id=71e1d0a4373f6cc5cd99e1400fb87d64d97c370f'>packages</a>/<a href='/guix/log/gnu/packages/bootloaders.scm?id=71e1d0a4373f6cc5cd99e1400fb87d64d97c370f'>bootloaders.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/packages/bootloaders.scm?id=71e1d0a4373f6cc5cd99e1400fb87d64d97c370f&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-07-19 00:05:01 +0300'>2024-07-19</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=4ee2a660e5f1362d3a72dcdc62ba8ff5612949da'>gnu: grub: Enable building on powerpc64le-linux.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2024-07-19 00:04:50 +0300'>2024-07-19</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=447be4aff8d40ac247f0c5bef7088229b5e20411'>gnu: grub-minimal: Don't override configure-flags.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2024-07-01 17:17:21 +0200'>2024-07-01</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=770659059be746bfa42eee2d9118031e5c7604e5'>gnu: grub: Fix use of mdadm.</a><span class='msg-avail'>...</span></td><td>Christopher Baines</td></tr>
<tr><td><span title='2024-06-24 08:51:41 -0400'>2024-06-24</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=b9c38f26f120e3e12b3bfbf29c6248a08fe1a62c'>gnu: grub: Remove input labels and use gexps.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2024-06-24 08:51:41 -0400'>2024-06-24</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=e6facbe069ba536a6bb9dffc582a78f982596be6'>gnu: grub: Update to 2.12.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2024-05-27 19:30:22 +0200'>2024-05-27</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=00384aedbc6a371aaf90ca344a446952fdd5a6b3'>gnu: grub: Ignore metadata-csum-seed feature of ext4.</a><span class='msg-avail'>...</span></td><td>Lars-Dominik Braun</td></tr>
<tr><td><span title='2024-05-22 11:15:30 +0800'>2024-05-22</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=08474ff6ecf9472b58d188ce2a03a1c4f3f1a146'>gnu: Add u-boot-starfive-visionfive2.</a><span class='msg-avail'>...</span></td><td>Zheng Junjie</td></tr>
<tr><td><span title='2024-03-28 17:39:42 +0200'>2024-03-28</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=daab3da5042a5803ffa13ee759b3f8895dd92de4'>gnu: u-boot-pine64-plus: Fix building on aarch64-linux.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2024-01-18 10:18:00 -0800'>2024-01-18</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=3e3975275bbab84d58f7740e9680b265769aa580'>gnu: u-boot: Update to 2024.01.</a><span class='msg-avail'>...</span></td><td>Herman Rimm</td></tr>
<tr><td><span title='2024-01-07 20:52:04 +0100'>2024-01-07</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=51735eac1cc21356dc1cb59356ebe96a460b5b59'>gnu: dtc: Update to 1.7.0.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2023-12-22 16:06:03 -0800'>2023-12-22</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=88fb95903c1d94b3be7e8a811d943af988041e4e'>gnu: bootloader: Add orangepi-r1-plus-lts-rk3328 bootloader.</a><span class='msg-avail'>...</span></td><td>Herman Rimm</td></tr>
<tr><td><span title='2023-12-22 16:05:50 -0800'>2023-12-22</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=fad93748cd2d44f7f68d2d973a22ed0b438e657b'>gnu: u-boot: Update to 2023.10.</a><span class='msg-avail'>...</span></td><td>Herman Rimm</td></tr>
<tr><td><span title='2023-11-24 13:34:00 -0800'>2023-11-24</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=4b6f6b3e180afc5d1b286130710dd9e3eb6c2889'>gnu: Add grub-coreboot</a><span class='msg-avail'>...</span></td><td>Denis 'GNUtoo' Carikli</td></tr>
<tr><td><span title='2023-10-22 16:09:04 -0400'>2023-10-22</span></td><td><a href='/guix/commit/gnu/packages/bootloaders.scm?id=f44fa21c3ec1d9bf1b9da009e1c795942bf654eb'>gnu: patman: Apply patch for new Change-Id setting.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>