Use ImportError rather than ModuleNotFoundError

Author: stasm

fluent/syntax/parser.py

@@ -6,10 +6,11 @@
 
 try:
     from __builtin__ import unichr as chr
-except ModuleNotFoundError:
+except ImportError:
     pass
 
 
+
 def with_span(fn):
     def decorated(self, ps, *args, **kwargs):
         if not self.with_spans: