The cantera_version should not be an option

SConstruct

@@ -549,7 +549,6 @@ config_options = [
            with a prefix like '/opt/cantera'. 'debian' installs to the stage
            directory in a layout used for generating Debian packages.""",
      defaults.fsLayout, ('standard','compact','debian')),
-    ('cantera_version', '', '2.3.0a1')
 ]
 
 opts.AddVariables(*config_options)
@@ -597,6 +596,7 @@ for arg in ARGUMENTS:
         sys.exit(1)
 
 # Require a StrictVersion-compatible version
+env['cantera_version'] = "2.3.0a1"
 ctversion = StrictVersion(env['cantera_version'])
 # MSI versions do not support pre-release tags
 env['cantera_msi_version'] = '.'.join(str(x) for x in ctversion.version)
@@ -782,8 +782,6 @@ def get_expression_value(includes, expression):
               '}\n'))
     return '\n'.join(s)
 
-configh = {}
-
 env['HAS_TIMES_H'] = conf.CheckCHeader('sys/times.h', '""')
 env['HAS_UNISTD_H'] = conf.CheckCHeader('unistd.h', '""')
 
@@ -1190,6 +1188,8 @@ else:
 # *** Set options needed in config.h ***
 # **************************************
 
+configh = {}
+
 configh['CANTERA_VERSION'] = quoted(env['cantera_version'])
 configh['CANTERA_SHORT_VERSION'] = quoted(env['cantera_short_version'])