Move calculation of normalised uri to the codepath where it is actually used

- this fixes a bug in the mako-render script which refuses to process a filename
  that is given as a relative path

mako/template.py

@@ -255,16 +255,6 @@ class Template(object):
             self.module_id = "memory:" + hex(id(self))
             self.uri = self.module_id
 
-        u_norm = self.uri
-        if u_norm.startswith("/"):
-            u_norm = u_norm[1:]
-        u_norm = os.path.normpath(u_norm)
-        if u_norm.startswith(".."):
-            raise exceptions.TemplateLookupException(
-                    "Template uri \"%s\" is invalid - "
-                    "it cannot be relative outside "
-                    "of the root path." % self.uri)
-
         self.input_encoding = input_encoding
         self.output_encoding = output_encoding
         self.encoding_errors = encoding_errors
@@ -310,6 +300,16 @@ class Template(object):
             if module_filename is not None:
                 path = module_filename
             elif module_directory is not None:
+                u_norm = self.uri
+                if u_norm.startswith("/"):
+                    u_norm = u_norm[1:]
+                u_norm = os.path.normpath(u_norm)
+                if u_norm.startswith(".."):
+                    raise exceptions.TemplateLookupException(
+                            "Template uri \"%s\" is invalid - "
+                            "it cannot be relative outside "
+                            "of the root path." % self.uri)
+
                 path = os.path.abspath(
                         os.path.join(
                             os.path.normpath(module_directory),