Fix compile errors reported by HP aCC by fixing bugs introduced in 6dc57e2a
which do not cause trouble on clang or GCC.

Patch by Michael Osipov.

The http_response() and https_response() methods of the HTTPErrorProcessor
class have two required parameters, 'request' and 'response'.

Read from data socket to avoid "[SSL] shutdown while in init" exception
during shutdown of the dummy server.
Signed-off-by: Christian Heimes <christian@python.org>


<!-- issue-number: [bpo-34391](https://www.bugs.python.org/issue34391) -->
https://bugs.python.org/issue34391
<!-- /issue-number -->

os.readlink() now accepts path-like and bytes objects on Windows.
Previously, support for path-like and bytes objects was only
implemented on Unix.

This commit also merges Unix and Windows implementations of
os.readlink() in one function and adds basic unit tests to increase
test coverage of the function.

Avoid undefined pointer arithmetic with NULL.

Downstream vendors have started to deprecate weak keys. Update all RSA keys
and DH params to use at least 2048 bits.

Finite field DH param file use RFC 7919 values, generated with

    certtool --get-dh-params --sec-param=high
Signed-off-by: Christian Heimes <christian@python.org>

Follow up to bpo-34270.

Fixes:
```
Lib/test/test_asyncio/test_tasks.py:330: DeprecationWarning: invalid escape sequence \d
  match1 = re.match("^<Task pending name='Task-(\d+)'", repr(t1))
Lib/test/test_asyncio/test_tasks.py:332: DeprecationWarning: invalid escape sequence \d
  match2 = re.match("^<Task pending name='Task-(\d+)'", repr(t2))
```

* SMTP.startssl: Fix doc on keyfile and certfile use

* SMTP.startssl: Add missing keyfile and certfile deprecation notice

* SMTP: Doc grammar fixes

Improves speed by 9 to 10ns per call.

Valgrind isn't seeing PyObject_Free/PyObject_Realloc, but using _PyObject_Free/_PyObject_Realloc works.

The main cause of this bug was fixed as part of bpo-31908.

The __getitem__ methods of DOMEventStream, FileInput,
and FileWrapper classes ignore their 'index' parameters
and return the next item instead.

In the documentation, the `env` directory is specified when we execute
the `make venv` command. But in the code, `make venv` will create the
virtualenv inside the `venv` directory (defined by `VENVDIR`)

Co-authored-by: Antti Haapala <antti.haapala@anttipatterns.com>

posixmodule.c always declares environ, so don't bother catching a NameError in os.py.

PyErr_Print() always clears the error indicator, so there is no need
to call PyErr_Clear() immediately afterwards.

Patch by Terry Jan Reedy.