Fix exception syntax for module.Exception cases.

This case wasn't catch at my first try.

lettuce/__init__.py

@@ -177,7 +177,7 @@ class Runner(object):
                                 random=self.random,
                                 failfast=self.failfast))
 
-        except exceptions.LettuceSyntaxError, e:
+        except exceptions.LettuceSyntaxError as e:
             sys.stderr.write(e.msg)
             failed = True
         except:

lettuce/registry.py

@@ -69,7 +69,7 @@ class StepDict(dict):
     def _assert_is_step(self, step, func):
         try:
             re.compile(step)
-        except re.error, e:
+        except re.error as e:
             raise StepLoadingError("Error when trying to compile:\n"
                                    "  regex: %r\n"
                                    "  for function: %s\n"