py/objstr: For str.endswith(s, start) raise NotImpl instead of assert.

py/objstr.c

@@ -699,7 +699,9 @@ STATIC mp_obj_t str_startswith(mp_uint_t n_args, const mp_obj_t *args) {
 STATIC mp_obj_t str_endswith(mp_uint_t n_args, const mp_obj_t *args) {
     GET_STR_DATA_LEN(args[0], str, str_len);
     GET_STR_DATA_LEN(args[1], suffix, suffix_len);
-    assert(n_args == 2);
+    if (n_args > 2) {
+        mp_not_implemented("start/end indices");
+    }
 
     if (suffix_len > str_len) {
         return mp_const_false;

tests/misc/non_compliant.py

@@ -52,6 +52,12 @@ try:
 except NotImplementedError:
     print('NotImplementedError')
 
+# str.endswith(s, start) not implemented
+try:
+    'abc'.endswith('c', 1)
+except NotImplementedError:
+    print('NotImplementedError')
+
 # bytes(...) with keywords not implemented
 try:
     bytes('abc', encoding='utf8')

tests/misc/non_compliant.py.exp

@@ -8,3 +8,4 @@ NotImplementedError
 NotImplementedError
 NotImplementedError
 NotImplementedError
+NotImplementedError