Issue #23439: Add missing entries to http.client.__all__.

Also, document the LineTooLong exception since it can be raised by
the members of public API (e.g. http.client.HTTPResponse).

Patch by Martin Panter.

Doc/library/http.client.rst

@@ -169,6 +169,12 @@ The following exceptions are raised as appropriate:
    status code that we don't understand.
 
 
+.. exception:: LineTooLong
+
+   A subclass of :exc:`HTTPException`.  Raised if an excessively long line
+   is received in the HTTP protocol from the server.
+
+
 The constants defined in this module are:
 
 .. data:: HTTP_PORT

Lib/http/client.py

@@ -75,12 +75,14 @@ import socket
 import collections
 from urllib.parse import urlsplit
 
+# HTTPMessage, parse_headers(), and the HTTP status code constants are
+# intentionally omitted for simplicity
 __all__ = ["HTTPResponse", "HTTPConnection",
            "HTTPException", "NotConnected", "UnknownProtocol",
            "UnknownTransferEncoding", "UnimplementedFileMode",
            "IncompleteRead", "InvalidURL", "ImproperConnectionState",
            "CannotSendRequest", "CannotSendHeader", "ResponseNotReady",
-           "BadStatusLine", "error", "responses"]
+           "BadStatusLine", "LineTooLong", "error", "responses"]
 
 HTTP_PORT = 80
 HTTPS_PORT = 443

Lib/test/test_httplib.py

@@ -920,7 +920,22 @@ class Readliner:
             self.remainder = b"".join(data)
             raise
 
+
 class OfflineTest(TestCase):
+    def test_all(self):
+        # Documented objects defined in the module should be in __all__
+        expected = {"responses"}  # White-list documented dict() object
+        # HTTPMessage, parse_headers(), and the HTTP status code constants are
+        # intentionally omitted for simplicity
+        blacklist = {"HTTPMessage", "parse_headers"}
+        for name in dir(client):
+            if name in blacklist:
+                continue
+            module_object = getattr(client, name)
+            if getattr(module_object, "__module__", None) == "http.client":
+                expected.add(name)
+        self.assertCountEqual(client.__all__, expected)
+
     def test_responses(self):
         self.assertEqual(client.responses[client.NOT_FOUND], "Not Found")