bpo-40267: Fix message when last input character produces a SyntaxError (GH-19521)

When there is a SyntaxError after reading the last input character from
the tokenizer and if no newline follows it, the error message used to be
`unexpected EOF while parsing`, which is wrong.

Tools/scripts/generate_token.py

@@ -69,6 +69,10 @@ extern "C" {
 #define ISTERMINAL(x)           ((x) < NT_OFFSET)
 #define ISNONTERMINAL(x)        ((x) >= NT_OFFSET)
 #define ISEOF(x)                ((x) == ENDMARKER)
+#define ISWHITESPACE(x)         ((x) == ENDMARKER || \\
+                                 (x) == NEWLINE   || \\
+                                 (x) == INDENT    || \\
+                                 (x) == DEDENT)
 
 
 PyAPI_DATA(const char * const) _PyParser_TokenNames[]; /* Token names */