Patch #439995 (slightly modified from the uploaded version):

Work around Linux's nonstandard nice() systemcall, which does not return the
new priority.

This closes SF bug #439990.

Modules/posixmodule.c

@@ -1121,8 +1121,25 @@ posix_nice(PyObject *self, PyObject *args)
 
 	if (!PyArg_ParseTuple(args, "i:nice", &increment))
 		return NULL;
+
+	/* There are two flavours of 'nice': one that returns the new
+	   priority (as required by almost all standards out there) and the
+	   Linux one, which returns '0' on success and advices the use of
+	   getpriority() to get the new priority.
+	   
+	   If we are of the nice family that returns the new priority, we
+	   need to clear errno before the call, and check if errno is filled
+	   before calling posix_error() on a returnvalue of -1, because the
+	   -1 may be the actual new priority! */
+
+	errno = 0;
 	value = nice(increment);
-	if (value == -1)
+#ifdef HAVE_GETPRIORITY
+	if (value == 0)
+		value = getpriority(PRIO_PROCESS, 0);
+#endif
+	if (value == -1 && errno != 0)
+		/* either nice() or getpriority() returned an error */
 		return posix_error();
 	return PyInt_FromLong((long) value);
 }

config.h.in

@@ -1,4 +1,4 @@
-/* config.h.in.  Generated automatically from configure.in by autoheader.  */
+/* config.h.in.  Generated automatically from configure.in by autoheader 2.13.  */
 
 /* Define if on AIX 3.
    System headers sometimes define this.
@@ -299,6 +299,9 @@
 /* The number of bytes in a wchar_t.  */
 #undef SIZEOF_WCHAR_T
 
+/* Define if you have the _getpty function.  */
+#undef HAVE__GETPTY
+
 /* Define if you have the alarm function.  */
 #undef HAVE_ALARM
 
@@ -392,8 +395,8 @@
 /* Define if you have the getpid function.  */
 #undef HAVE_GETPID
 
-/* Define if you have the _getpty function.  */
-#undef HAVE__GETPTY
+/* Define if you have the getpriority function.  */
+#undef HAVE_GETPRIORITY
 
 /* Define if you have the getpwent function.  */
 #undef HAVE_GETPWENT
@@ -557,14 +560,14 @@
 /* Define if you have the waitpid function.  */
 #undef HAVE_WAITPID
 
-/* Define if you have the <db_185.h> header file.  */
-#undef HAVE_DB_185_H
+/* Define if you have the <db.h> header file.  */
+#undef HAVE_DB_H
 
 /* Define if you have the <db1/ndbm.h> header file.  */
 #undef HAVE_DB1_NDBM_H
 
-/* Define if you have the <db.h> header file.  */
-#undef HAVE_DB_H
+/* Define if you have the <db_185.h> header file.  */
+#undef HAVE_DB_185_H
 
 /* Define if you have the <dirent.h> header file.  */
 #undef HAVE_DIRENT_H

configure.in

@@ -1175,7 +1175,7 @@ AC_CHECK_FUNCS(alarm chown clock confstr ctermid ctermid_r execv \
  setlocale setregid setreuid setsid setpgid setuid setvbuf \
  sigaction siginterrupt sigrelse strftime strptime symlink sysconf \
  tcgetpgrp tcsetpgrp tempnam timegm times tmpfile tmpnam tmpnam_r \
- truncate uname waitpid _getpty)
+ truncate uname waitpid _getpty getpriority)
 
 # check for openpty and forkpty