Improve error message for '.

Author: serhiy-storchaka

Lib/test/test_format.py

@@ -278,8 +278,6 @@ def test_common_format(self):
                         "unsupported format %z at position 4")
         test_exc_common("abc %Id", 1, ValueError,
                         "unsupported format %I at position 4")
-        test_exc_common("abc %'d", 1, ValueError,
-                        "stray % at position 4 or unexpected format character ''' at position 5")
         test_exc_common("abc %1 d", 1, ValueError,
                         "stray % at position 4 or unexpected format character ' ' at position 6")
         test_exc_common('abc % (x)r', {}, ValueError,
@@ -363,6 +361,8 @@ def test_str_format(self):
             print('Testing exceptions')
         test_exc('abc %b', 1, ValueError,
                  "unsupported format %b at position 4")
+        test_exc("abc %'d", 1, ValueError,
+                 "stray % at position 4 or unexpected format character ''' (U+0027) at position 5")
         test_exc("abc %\nd", 1, ValueError,
                  "stray % at position 4 or unexpected format character U+000A at position 5")
         test_exc("abc %\x1fd", 1, ValueError,
@@ -465,6 +465,8 @@ def __bytes__(self):
             print('Testing exceptions')
         test_exc(b"abc %\nd", 1, ValueError,
                  "stray % at position 4 or unexpected format character with code 0x0a at position 5")
+        test_exc(b"abc %'d", 1, ValueError,
+                 "stray % at position 4 or unexpected format character with code 0x27 at position 5")
         test_exc(b"abc %\x1fd", 1, ValueError,
                  "stray % at position 4 or unexpected format character with code 0x1f at position 5")
         test_exc(b"abc %\x7fd", 1, ValueError,

Objects/bytesobject.c

@@ -1012,7 +1012,7 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
                                  "unsupported format %%%c at position %zd",
                                  c, (Py_ssize_t)(fmtstart - format - 1));
                 }
-                else if (c >= 32 && c < 127) {
+                else if (c >= 32 && c < 127 && c != '\'') {
                     PyErr_Format(PyExc_ValueError,
                                  "stray %% at position %zd or unexpected "
                                  "format character '%c' "

Objects/unicode_format.c

@@ -768,7 +768,7 @@ unicode_format_arg_format(struct unicode_formatter_t *ctx,
                          "unsupported format %%%c at position %zd",
                          (int)arg->ch, arg->fmtstart);
         }
-        else if (arg->ch >= 32 && arg->ch < 127) {
+        else if (arg->ch >= 32 && arg->ch < 127 && arg->ch != '\'') {
             PyErr_Format(PyExc_ValueError,
                          "stray %% at position %zd or unexpected "
                          "format character '%c' at position %zd",