catch errors in build time pkg-config parsing - closes #738

SConstruct

@@ -281,7 +281,7 @@ opts.AddVariables(
     ('CC', 'The C compiler used for configure checks of C libs (defaults to gcc).', 'gcc'),
     ('CUSTOM_CXXFLAGS', 'Custom C++ flags, e.g. -I<include dir> if you have headers in a nonstandard directory <include dir>', ''),
     ('CUSTOM_LDFLAGS', 'Custom linker flags, e.g. -L<lib dir> if you have libraries in a nonstandard directory <lib dir>', ''),
-    EnumVariable('OPTIMIZATION','Set g++ optimization level','2', ['0','1','2','3','4']),
+    EnumVariable('OPTIMIZATION','Set g++ optimization level','2', ['0','1','2','3','4','s']),
     # Note: setting DEBUG=True will override any custom OPTIMIZATION level
     BoolVariable('DEBUG', 'Compile a debug version of Mapnik', 'False'),
     BoolVariable('XML_DEBUG', 'Compile a XML verbose debug version of mapnik', 'False'),

src/SConscript

@@ -21,6 +21,7 @@
 
 
 import os
+import sys
 import glob
 from subprocess import Popen, PIPE
 
@@ -185,6 +186,7 @@ if True : # agg backend
 
 if env['HAS_CAIRO']:
     # attach libs to library linking environment
+    try:
         lib_env.ParseConfig('pkg-config --libs cairomm-1.0')
         env2 = lib_env.Clone()
         env2.Append(CXXFLAGS = '-DHAVE_CAIRO')
@@ -195,6 +197,9 @@ if env['HAS_CAIRO']:
             if cpp in source:
                 source.remove(cpp)
             source.insert(0,env2.SharedObject(cpp))
+    except OSError, e:
+        print '\nFailed to detect cairo/cairomm configuration, please re-run "python scons/scons.py configure"'
+        sys.exit(1)        
 
 if env['XMLPARSER'] == 'tinyxml':
     source += Split(