Enhance message for UnicodeEncodeError and UnicodeTranslateError.

If there is only one bad character it will now be printed in a
form that is a valid Python string.

Lib/test/test_codeccallbacks.py

@@ -258,7 +258,7 @@ class CodecCallbackTest(unittest.TestCase):
         self.check_exceptionobjectargs(
             UnicodeEncodeError,
             ["ascii", u"g\xfcrk", 1, 2, "ouch"],
-            "'ascii' codec can't encode character '\ufc' in position 1: ouch"
+            "'ascii' codec can't encode character '\\xfc' in position 1: ouch"
         )
         self.check_exceptionobjectargs(
             UnicodeEncodeError,
@@ -268,8 +268,24 @@ class CodecCallbackTest(unittest.TestCase):
         self.check_exceptionobjectargs(
             UnicodeEncodeError,
             ["ascii", u"\xfcx", 0, 1, "ouch"],
-            "'ascii' codec can't encode character '\ufc' in position 0: ouch"
+            "'ascii' codec can't encode character '\\xfc' in position 0: ouch"
         )
+        self.check_exceptionobjectargs(
+            UnicodeEncodeError,
+            ["ascii", u"\u0100x", 0, 1, "ouch"],
+            "'ascii' codec can't encode character '\\u0100' in position 0: ouch"
+        )
+        self.check_exceptionobjectargs(
+            UnicodeEncodeError,
+            ["ascii", u"\uffffx", 0, 1, "ouch"],
+            "'ascii' codec can't encode character '\\uffff' in position 0: ouch"
+        )
+        if sys.maxunicode > 0xffff:
+            self.check_exceptionobjectargs(
+                UnicodeEncodeError,
+                ["ascii", u"\U00010000x", 0, 1, "ouch"],
+                "'ascii' codec can't encode character '\\U00010000' in position 0: ouch"
+            )
 
     def test_unicodedecodeerror(self):
         self.check_exceptionobjectargs(
@@ -287,8 +303,24 @@ class CodecCallbackTest(unittest.TestCase):
         self.check_exceptionobjectargs(
             UnicodeTranslateError,
             [u"g\xfcrk", 1, 2, "ouch"],
-            "can't translate character '\\ufc' in position 1: ouch"
+            "can't translate character '\\xfc' in position 1: ouch"
         )
+        self.check_exceptionobjectargs(
+            UnicodeTranslateError,
+            [u"g\u0100rk", 1, 2, "ouch"],
+            "can't translate character '\\u0100' in position 1: ouch"
+        )
+        self.check_exceptionobjectargs(
+            UnicodeTranslateError,
+            [u"g\uffffrk", 1, 2, "ouch"],
+            "can't translate character '\\uffff' in position 1: ouch"
+        )
+        if sys.maxunicode > 0xffff:
+            self.check_exceptionobjectargs(
+                UnicodeTranslateError,
+                [u"g\U00010000rk", 1, 2, "ouch"],
+                "can't translate character '\\U00010000' in position 1: ouch"
+            )
         self.check_exceptionobjectargs(
             UnicodeTranslateError,
             [u"g\xfcrk", 1, 3, "ouch"],

Python/exceptions.c

@@ -1251,10 +1251,18 @@ UnicodeEncodeError__str__(PyObject *self, PyObject *arg)
 	goto error;
 
     if (end==start+1) {
+	int badchar = (int)PyUnicode_AS_UNICODE(objectObj)[start];
+	char *format;
+	if (badchar <= 0xff)
+	   format = "'%.400s' codec can't encode character '\\x%02x' in position %d: %.400s";
+	else if (badchar <= 0xffff)
+	   format = "'%.400s' codec can't encode character '\\u%04x' in position %d: %.400s";
+	else
+	   format = "'%.400s' codec can't encode character '\\U%08x' in position %d: %.400s";
 	PyOS_snprintf(buffer, sizeof(buffer),
-	    "'%.400s' codec can't encode character '\\u%x' in position %d: %.400s",
+	    format,
 	    PyString_AS_STRING(encodingObj),
-	    (int)PyUnicode_AS_UNICODE(objectObj)[start],
+	    badchar,
 	    start,
 	    PyString_AS_STRING(reasonObj)
 	);
@@ -1329,7 +1337,7 @@ UnicodeDecodeError__str__(PyObject *self, PyObject *arg)
 
     if (end==start+1) {
 	PyOS_snprintf(buffer, sizeof(buffer),
-	    "'%.400s' codec can't decode byte 0x%x in position %d: %.400s",
+	    "'%.400s' codec can't decode byte 0x%02x in position %d: %.400s",
 	    PyString_AS_STRING(encodingObj),
 	    ((int)PyString_AS_STRING(objectObj)[start])&0xff,
 	    start,
@@ -1438,9 +1446,17 @@ UnicodeTranslateError__str__(PyObject *self, PyObject *arg)
 	goto error;
 
     if (end==start+1) {
+	int badchar = (int)PyUnicode_AS_UNICODE(objectObj)[start];
+	char *format;
+	if (badchar <= 0xff)
+	   format = "can't translate character '\\x%02x' in position %d: %.400s";
+	else if (badchar <= 0xffff)
+	   format = "can't translate character '\\u%04x' in position %d: %.400s";
+	else
+	   format = "can't translate character '\\U%08x' in position %d: %.400s";
 	PyOS_snprintf(buffer, sizeof(buffer),
-	    "can't translate character '\\u%x' in position %d: %.400s",
-	    (int)PyUnicode_AS_UNICODE(objectObj)[start],
+	    format,
+	    badchar,
 	    start,
 	    PyString_AS_STRING(reasonObj)
 	);