Upstream PR:
https://github.com/codership/galera/pull/512

diff -up galera-25.3.23/SConstruct.bak galera-25.3.23/SConstruct
--- galera-25.3.23/SConstruct.bak	2018-07-13 15:14:49.059835554 +0200
+++ galera-25.3.23/SConstruct	2018-07-13 15:19:07.717967794 +0200
@@ -194,8 +194,8 @@ if link != 'default':
     env.Replace(LINK = link)
 
 # Get compiler name/version, CXX may be set to "c++" which may be clang or gcc
-cc_version = str(read_first_line(env['CC'].split() + ['--version']))
-cxx_version = str(read_first_line(env['CXX'].split() + ['--version']))
+cc_version = str(read_first_line(env['CC'].split() + ['--version']).decode())
+cxx_version = str(read_first_line(env['CXX'].split() + ['--version']).decode())
 
 print('Using C compiler executable: ' + env['CC'])
 print('C compiler version is: ' + cc_version)