gh-102541: Fix Helper.help("mod") for non-existent mod

[Eclips4]

If the output arg to Helper() is a stream rather than the default None, which means 'page to stdout', the ImportError from pydoc.resolve is currently not caught in `pydoc.doc. The same error is caught when output is None.

import pydoc
from io import StringIO

input = StringIO()
output = StringIO()
help = pydoc.Helper(input, output)
help.help("abd")
input.close()
output.close()

Traceback:

./python example.py
Running debug|x64 interpreter...
Traceback (most recent call last):
  File "C:\Users\KIRILL-1\CLionProjects\cpython\example.py", line 7, in <module>
    help.help("abd", is_cli=True)
  File "C:\Users\KIRILL-1\CLionProjects\cpython\Lib\pydoc.py", line 2067, in help
    elif request: doc(request, 'Help on %s:', output=self._output, is_cli=is_cli)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\KIRILL-1\CLionProjects\cpython\Lib\pydoc.py", line 1793, in doc
    output.write(render_doc(thing, title, forceload, plaintext))
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\KIRILL-1\CLionProjects\cpython\Lib\pydoc.py", line 1760, in render_doc
    object, name = resolve(thing, forceload)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\KIRILL-1\CLionProjects\cpython\Lib\pydoc.py", line 1746, in resolve
    raise ImportError('''\
ImportError: No Python documentation found for 'abd'.
Use help() to get the interactive help utility.
Use help(str) for help on the str class.

EDITED by terryjreedy July 1, 2023 to better describe the issue, so I could review the patch,
and show the current result after the merge of the first PR for the issue. Instead of the last line
there were about 15 lines that repeated the Traceback.

• Issue: help CLI shows a traceback when import failed #102541

[Eclips4]

cc @corona10

[corona10]

@terryjreedy @Yhg1s @ambv

I am out of OSS for this month. If this PR is urgent, I would like to request reviewing of this PR to other reviewers.

[miss-islington]

Thanks @Eclips4 for the PR, and @terryjreedy for merging it 🌮🎉.. I'm working now to backport this PR to: 3.11, 3.12.
🐍🍒⛏🤖

[bedevere-bot]

GH-106322 is a backport of this pull request to the 3.12 branch.

[bedevere-bot]

GH-106323 is a backport of this pull request to the 3.11 branch.