compare singletons by identity not equality (closes #16712)

Patch from Serhiy Storchaka.
diff --git a/Lib/pydoc.py b/Lib/pydoc.py
index aa296c4..fa531e9 100755
--- a/Lib/pydoc.py
+++ b/Lib/pydoc.py
@@ -2551,8 +2551,8 @@
             if opt == '-w':
                 writing = True
 
-        if start_server == True:
-            if port == None:
+        if start_server:
+            if port is None:
                 port = 0
             browse(port, open_browser=open_browser)
             return