[python mode] Parse ... as an operator

To avoid treating it like 3 separate dot tokens

Closes #5861

mode/python/python.js

@@ -44,7 +44,7 @@
     var delimiters = parserConf.delimiters || parserConf.singleDelimiters || /^[\(\)\[\]\{\}@,:`=;\.\\]/;
     //               (Backwards-compatiblity with old, cumbersome config system)
     var operators = [parserConf.singleOperators, parserConf.doubleOperators, parserConf.doubleDelimiters, parserConf.tripleDelimiters,
-                     parserConf.operators || /^([-+*/%\/&|^]=?|[<>=]+|\/\/=?|\*\*=?|!=|[~!@])/]
+                     parserConf.operators || /^([-+*/%\/&|^]=?|[<>=]+|\/\/=?|\*\*=?|!=|[~!@]|\.\.\.)/]
     for (var i = 0; i < operators.length; i++) if (!operators[i]) operators.splice(i--, 1)
 
     var hangingIndent = parserConf.hangingIndent || conf.indentUnit;