Merge pull request #3252 from Vladimir-Chan/master

make Python2 runtime keep consistent with Java

runtime/Python2/src/antlr4/BufferedTokenStream.py

@@ -196,17 +196,17 @@ def setTokenSource(self, tokenSource):
 
 
     # Given a starting index, return the index of the next token on channel.
-    #  Return i if tokens[i] is on channel.  Return -1 if there are no tokens
-    #  on channel between i and EOF.
+    #  Return i if tokens[i] is on channel.  Return the index of the EOF toekn
+    #  if there are no tokens on channel between i and EOF.
     #/
     def nextTokenOnChannel(self, i, channel):
         self.sync(i)
         if i>=len(self.tokens):
-            return -1
+            return len(self.tokens) - 1
         token = self.tokens[i]
         while token.channel!=channel:
             if token.type==Token.EOF:
-                return -1
+                return i
             i += 1
             self.sync(i)
             token = self.tokens[i]