[SCons] Fix build errors when path to Python contains spaces

SConstruct

@@ -888,6 +888,8 @@ if env['VERBOSE']:
     print open('config.log').read()
     print '--------------------- end config.log ---------------------'
 
+env['python_cmd_esc'] = quoted(env['python_cmd'])
+
 # Python 2 Package Settings
 cython_min_version = LooseVersion('0.17')
 env['install_python2_action'] = ''
@@ -1270,7 +1272,7 @@ for cti in mglob(env, 'data/inputs', 'cti'):
     outName = os.path.splitext(cti.name)[0] + '.xml'
     convertedInputFiles.add(outName)
     build(env.Command('build/data/%s' % outName, cti.path,
-                      '$python_cmd interfaces/cython/cantera/ctml_writer.py $SOURCE $TARGET'))
+                      '$python_cmd_esc interfaces/cython/cantera/ctml_writer.py $SOURCE $TARGET'))
 
 
 # Copy input files which are not present as cti:

interfaces/cython/SConscript

@@ -159,7 +159,7 @@ if localenv['python_package'] == 'full':
     py2env['py_extension'] = ext[0].name
     py2env.SubstFile('setup2.py', 'setup.py.in')
     build_cmd = ('cd interfaces/cython &&'
-                 ' $python_cmd setup2.py build --build-lib=../../build/python2')
+                 ' $python_cmd_esc setup2.py build --build-lib=../../build/python2')
     mod = build(py2env.Command('#build/python2/cantera/__init__.py',
                                'setup2.py',
                                build_cmd))

interfaces/python_minimal/SConscript

@@ -27,7 +27,7 @@ for script in ['ctml_writer', 'ck2cti']:
     localenv['py_%s' % script] = repr('scripts/%s%s' % (script, script_ext))
 
 build_cmd = ('cd interfaces/python_minimal &&'
-             ' $python_cmd setup.py build --build-lib=../../build/python2')
+             ' $python_cmd_esc setup.py build --build-lib=../../build/python2')
 
 mod = build(localenv.Command('#build/python2/cantera/__init__.py',
                              'setup.py',