Issue #11303: Added shortcuts for utf8 and latin1 encodings.
Documented the list of optimized encodings as CPython implementation
detail.
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index e7bbd80..48ea0a2 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -1462,13 +1462,15 @@
     char lower[11];  /* Enough for any encoding shortcut */
 
     if (encoding == NULL)
-        encoding = PyUnicode_GetDefaultEncoding();
+        return PyUnicode_DecodeUTF8(s, size, errors);
 
     /* Shortcuts for common default encodings */
     if (normalize_encoding(encoding, lower, sizeof(lower))) {
-        if (strcmp(lower, "utf-8") == 0)
+        if ((strcmp(lower, "utf-8") == 0) ||
+            (strcmp(lower, "utf8") == 0))
             return PyUnicode_DecodeUTF8(s, size, errors);
         else if ((strcmp(lower, "latin-1") == 0) ||
+                 (strcmp(lower, "latin1") == 0) ||
                  (strcmp(lower, "iso-8859-1") == 0))
             return PyUnicode_DecodeLatin1(s, size, errors);
 #if defined(MS_WINDOWS) && defined(HAVE_USABLE_WCHAR_T)
@@ -1670,15 +1672,19 @@
     }
 
     if (encoding == NULL)
-        encoding = PyUnicode_GetDefaultEncoding();
+        return PyUnicode_EncodeUTF8(PyUnicode_AS_UNICODE(unicode),
+                                    PyUnicode_GET_SIZE(unicode),
+                                    errors);
 
     /* Shortcuts for common default encodings */
     if (normalize_encoding(encoding, lower, sizeof(lower))) {
-        if (strcmp(lower, "utf-8") == 0)
+        if ((strcmp(lower, "utf-8") == 0) ||
+            (strcmp(lower, "utf8") == 0))
             return PyUnicode_EncodeUTF8(PyUnicode_AS_UNICODE(unicode),
                                         PyUnicode_GET_SIZE(unicode),
                                         errors);
         else if ((strcmp(lower, "latin-1") == 0) ||
+                 (strcmp(lower, "latin1") == 0) ||
                  (strcmp(lower, "iso-8859-1") == 0))
             return PyUnicode_EncodeLatin1(PyUnicode_AS_UNICODE(unicode),
                                           PyUnicode_GET_SIZE(unicode),