Added SystemError as possible compiling error

Python.org Python raises a SystemError for a missing compiler when
running "customize_compiler" so before the "build_extension" method for
which other errors get trapped. Look also for SystemError when running
build_ext.run method to check for this.
diff --git a/setup.py b/setup.py
index d7bb2c3..07bb16f 100644
--- a/setup.py
+++ b/setup.py
@@ -22,11 +22,16 @@
         pass
 
 
+# Known errors when running build_ext.build_extension method
 ext_errors = (CCompilerError, DistutilsExecError, DistutilsPlatformError)
 if sys.platform == 'win32' and sys.version_info > (2, 6):
     # 2.6's distutils.msvc9compiler can raise an IOError when failing to
     # find the compiler
     ext_errors += (IOError,)
+# Known errors when running build_ext.run method
+run_errors = (DistutilsPlatformError,)
+if sys.platform == 'darwin':
+    run_errors += (SystemError,)
 
 
 class BuildFailed(Exception):
@@ -39,7 +44,7 @@
     def run(self):
         try:
             build_ext.run(self)
-        except DistutilsPlatformError:
+        except run_errors:
             raise BuildFailed()
 
     def build_extension(self, ext):