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'])
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<div class='path'>path: <a href='/guix/log/?id=b6021d38ab215a9de25df3d4131e5cc681e22895'>root</a>/<a href='/guix/log/m4?id=b6021d38ab215a9de25df3d4131e5cc681e22895'>m4</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/m4?id=b6021d38ab215a9de25df3d4131e5cc681e22895&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-01-14 11:41:15 +0200'>2022-01-14</span></td><td><a href='/guix/commit/m4?id=03b45230d409c5f09e6ad18f23f313a13dbddb7d'>gnu: bootstrap: Add support for riscv64-linux.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2021-12-14 18:33:49 +0200'>2021-12-14</span></td><td><a href='/guix/commit/m4?id=08d15a24c90e597f1656c3c0c3dbccf2022517de'>build: Adjust 'courage level' of different systems.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2021-05-23 22:23:18 +0300'>2021-05-23</span></td><td><a href='/guix/commit/m4?id=cbdb7d4fea928febc105985c03b8fb5d6eda3d27'>gnu: bootstrap: Add support for powerpc-linux.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2021-03-23 23:19:57 -0700'>2021-03-23</span></td><td><a href='/guix/commit/m4?id=a16eb6c5f97f136b678540ba61f12b2c08e43e13'>Add powerpc64le-linux as a supported Guix architecture.</a><span class='msg-avail'>...</span></td><td>Chris Marusich</td></tr>
<tr><td><span title='2021-03-17 12:03:23 +0100'>2021-03-17</span></td><td><a href='/guix/commit/m4?id=62a091368df3bab499142d06f5114a73915c71f2'>maint: Check whether Guile-zlib is recent enough.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-02-04 09:23:39 +0100'>2021-02-04</span></td><td><a href='/guix/commit/m4?id=55daad123e896c0e83361496cf49625289ee3571'>build: Add '--with-channel-commit' and related configure flags.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-12-11 19:06:53 +0100'>2020-12-11</span></td><td><a href='/guix/commit/m4?id=dbdae9f96f11a006993b659e0e7fd5cbf467f844'>maint: Avoid macros obsolete in Autoconf 2.70.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-10-22 17:10:25 +0200'>2020-10-22</span></td><td><a href='/guix/commit/m4?id=59bb1ae3a9aeae75a75b20090253613a7a8800d8'>git: Require Guile-Git 0.3.0 or later.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-09-08 00:47:35 +0200'>2020-09-08</span></td><td><a href='/guix/commit/m4?id=b5eb901ab508e13a10d8c11fe0c9d0d06dddce96'>Remove (guix json) and require Guile-JSON 4.3.0+.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-08-29 16:24:17 +0200'>2020-08-29</span></td><td><a href='/guix/commit/m4?id=f5d3a1690cb78ce9413b78352f1030bf4801617a'>build: Remove check for Guile 2.2.1 bug.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-08-24 13:35:24 +0200'>2020-08-24</span></td><td><a href='/guix/commit/m4?id=4c0c65acfade63ce0549115d19db4b639c1e9992'>Use "guile-zlib" and "guile-lzlib" instead of (guix config).</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2020-07-20 23:25:09 +0200'>2020-07-20</span></td><td><a href='/guix/commit/m4?id=e8088f0b06c2193f2cce04a48aa1350229442a9f'>ssh: Speed up RPCs by using #:nodelay.</a><span class='msg-avail'>...</span></td><td>Lars-Dominik Braun</td></tr>
<tr><td><span title='2020-05-28 11:12:40 +0300'>2020-05-28</span></td><td><a href='/guix/commit/m4?id=03e6404936ef0974fdbc877d537b97b28e54124d'>doc: Remove explicit support for mips64el-linux.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2020-05-28 00:55:00 +0200'>2020-05-28</span></td><td><a href='/guix/commit/m4?id=c1dc50ab202fafedde3a6b70ce6339496ad53a51'>maint: Check whether Guile-Gcrypt is recent enough.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-02-22 00:45:58 +0100'>2020-02-22</span></td><td><a href='/guix/commit/m4?id=378918725259d221222dd0b1831fbaa3e0a17e1f'>build: Depend on guile-ssh 0.12.0</a><span class='msg-avail'>...</span></td><td>Lars-Dominik Braun</td></tr>
<tr><td><span title='2019-08-17 19:26:21 +0200'>2019-08-17</span></td><td><a href='/guix/commit/m4?id=611a64bd7e0893057cd04dcdc2a8d5e7ecc39e45'>build: 'GUIX_CHECK_GUILE_JSON' really checks for Guile-JSON 3.x.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-07-25 00:16:41 +0200'>2019-07-25</span></td><td><a href='/guix/commit/m4?id=81c3dc32244a17241d74eea9fa265edfcb326f6d'>maint: Switch to Guile-JSON 3.x.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-05-06 23:21:33 +0200'>2019-05-06</span></td><td><a href='/guix/commit/m4?id=fea338c6ca1922097fa233be85f424c152a4f507'>Add (guix lzlib).</a><span class='msg-avail'>...</span></td><td>Pierre Neidhardt</td></tr>