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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<tr><td><span title='2022-11-15 12:16:43 +0100'>2022-11-15</span></td><td><a href='/guix/commit/gnu/installer/hardware.scm?id=514fedbf3966b7fbab31a6c63b4210ec8b5b0c9a'>installer: Report known-unsupported PCI devices.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/hardware.scm: New file.
* gnu/local.mk (INSTALLER_MODULES): Add it.
* po/guix/POTFILES.in: Add it.
* gnu/installer.scm (installer-steps): Pass #:pci-database to the
'welcome' step procedure.
* gnu/installer/newt.scm (welcome-page): Add #:pci-database and pass it
to 'run-welcome-page'.
* gnu/installer/newt/welcome.scm (check-hardware-support): Add #:pci-database.
Enumerate unsupported PCI devices and run an error page when unsupported
devices are found.
(run-welcome-page): Add #:pci-database and pass it to
'check-hardware-support' and to the recursive call.
* gnu/installer/record.scm (&lt;installer&gt;)[welcome-page]: Adjust comment.
* doc/guix.texi (Hardware Considerations): Mention it.
</span></span></td><td>Ludovic Courtès</td></tr>
2-11</span></td><td><a href='/guix/commit/HACKING?id=6701edbfad62ba9572ffd35497df3db27b208ba5'>HACKING: Update key server.</a><span class='msg-avail'>...<span class='msg-tooltip'>* HACKING (Commit Access): Recommend pool.sks-keyservers.net.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-07-22 17:00:47 +0200'>2018-07-22</span></td><td><a href='/guix/commit/HACKING?id=5285192150c83db12136af6a123e03bb9b9dbe5f'>doc: Fix typo (missing period)</a><span class='msg-avail'>...<span class='msg-tooltip'>* HACKING (Commit Access): Fix typo.
</span></span></td><td>Pierre Neidhardt</td></tr>
<tr><td><span title='2017-08-19 13:42:52 +0530'>2017-08-19</span></td><td><a href='/guix/commit/HACKING?id=acabbd597678e1f0be995297bb009b6dd38ae795'>doc: Mention how to use emacs-debbugs.</a><span class='msg-avail'>...<span class='msg-tooltip'>* HACKING (Using emacs-debbugs): Add section on using emacs-debbugs.
</span></span></td><td>Arun Isaac</td></tr>