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='2022-07-16 23:25:18 +0200'>2022-07-16</span></td><td><a href='/guix/commit/gnu/packages/patches/ghostscript-no-header-creationdate.patch?id=22b9a056ea0ebc77bd191e486f0bf3d1263add5b'>gnu: ghostscript: Update to 9.56.1.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/ghostscript.scm (ghostscript): Update to 9.56.1.
[arguments]: Remove #:parallel-tests?.  Remove trailing #t's.
* gnu/packages/patches/ghostscript-no-header-creationdate.patch,
gnu/packages/patches/ghostscript-no-header-id.patch,
gnu/packages/patches/ghostscript-no-header-uuid.patch: Rebase on 9.56.1.
</span></span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2021-07-19 12:43:15 +0200'>2021-07-19</span></td><td><a href='/guix/commit/gnu/packages/patches/ghostscript-no-header-creationdate.patch?id=db5962c68099f835350c24c8a3f889b9fa1f8a8e'>gnu: ghostscript: Improve reproducibility of PDF document generation</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/patches/ghostscript-no-header-creationdate.patch: Disable
  writing "xmp:ModifyDate" and "xmp:CreateDate" if GS_GENERATE_UUIDS is set to
  "0" or "no".
</span></span></td><td>Guillaume Le Vaillant</td></tr>