modernize some modules' code by replacing OSError->ENOENT/ENOTDIR/EPERM/EEXIST occurrences with the corresponding pep-3151 exceptions (FileNotFoundError, NotADirectoryError, etc.)
diff --git a/Lib/smtpd.py b/Lib/smtpd.py
index 1e239a1..3cab264 100755
--- a/Lib/smtpd.py
+++ b/Lib/smtpd.py
@@ -850,8 +850,7 @@
         nobody = pwd.getpwnam('nobody')[2]
         try:
             os.setuid(nobody)
-        except OSError as e:
-            if e.errno != errno.EPERM: raise
+        except PermissionError:
             print('Cannot setuid "nobody"; try running with -n option.', file=sys.stderr)
             sys.exit(1)
     try: