Fix #340: Always use raw strings for token regex (#341)

Author: glx22

nml/tokens.py

@@ -195,7 +195,7 @@ def t_ignore_comment(self, t):
         self.increment_lines(t.value.count("\n"))
 
     def t_ignore_whitespace(self, t):
-        "[ \t\r]+"
+        r"[ \t\r]+"
         pass
 
     def t_line_directive1(self, t):