Disable the parser hacks that enabled the "yield" keyword using a future
statement.
diff --git a/Python/ceval.c b/Python/ceval.c
index ec62350..5e67b29 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -2984,10 +2984,12 @@
 			result = 1;
 			cf->cf_flags |= compilerflags;
 		}
+#if 0 /* future keyword */
 		if (codeflags & CO_GENERATOR_ALLOWED) {
 			result = 1;
 			cf->cf_flags |= CO_GENERATOR_ALLOWED;
 		}
+#endif
 	}
 	return result;
 }