fix Python 3 incompatibilities in SConstruct file

libserf-python3.patch

@@ -0,0 +1,30 @@
+diff -up serf-1.3.9/SConstruct.python3 serf-1.3.9/SConstruct
+--- serf-1.3.9/SConstruct.python3	2018-07-02 17:21:47.331685070 +0200
++++ serf-1.3.9/SConstruct	2018-07-02 17:27:12.316413515 +0200
+@@ -20,6 +20,8 @@
+ # ====================================================================
+ #
+ 
++from __future__ import print_function
++
+ import sys
+ import os
+ import re
+@@ -166,7 +168,7 @@ env.Append(BUILDERS = {
+ match = re.search('SERF_MAJOR_VERSION ([0-9]+).*'
+                   'SERF_MINOR_VERSION ([0-9]+).*'
+                   'SERF_PATCH_VERSION ([0-9]+)',
+-                  env.File('serf.h').get_contents(),
++                  env.File('serf.h').get_contents().decode('utf-8'),
+                   re.DOTALL)
+ MAJOR, MINOR, PATCH = [int(x) for x in match.groups()]
+ env.Append(MAJOR=str(MAJOR))
+@@ -183,7 +185,7 @@ CALLOUT_OKAY = not (env.GetOption('clean
+ 
+ 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'])

libserf.spec

@@ -17,6 +17,7 @@ BuildRequires:  gcc, %{scons_pkg}, pkgconfig
 BuildRequires:  apr-devel, apr-util-devel, krb5-devel, openssl-devel
 BuildRequires:  zlib-devel
 Patch0:         %{name}-norpath.patch
+Patch1:         %{name}-python3.patch
 
 %description
 The serf library is a C-based HTTP client library built upon the Apache