This used expect_re with a regex ending in `.*`, followed by an
`expect_prompt`.
This meant that, depending on the timing, the regex could swallow the
prompt marker, which caused extremely confusing output like
>Testing file pexpects/generic.py:Failed to match pattern: prompt 14
> ...
> OUTPUT +1.33 ms (Line 70): \rprompt 13>functions\r\nN_, abbr,
> alias, bg, cd, [SNIP], up-or-search, vared, wait\r\n⏎
> \r⏎ \r\rprompt 14>
Yeah - it shows that "prompt 14" was in the output and it can't find
"prompt 14".
I could reproduce the failure locally when running the tests
repeatedly. I got one after 17 attempts and so far haven't been able
to reproduce it with this change applied.
Don't go into implicit interactive mode without ever executing
anything - not even `exit` or reacting to ctrl-d. That just renders
the shell useless and unquittable.
I *think* this might sometimes (on CI) be eating the prompt, so that the actual `prompt`
part of `expect_prompt` doesn't find anything.
On Github Actions we see things like:
```
Testing file pexpects/generic.py ... Failed to match pattern: prompt 5
generic.py:35: timeout from expect_prompt("echo .history.*")
[...]
OUTPUT +1.08 ms (Line 31): \rprompt 4>
INPUT +0.35 ms (Line 34): echo $history[1]\n
OUTPUT +1.58 ms (Line 35): echo $history[1]\r\necho $history[1]\r\n⏎ \r⏎ \r\rprompt 5>
```
so the prompt *is* printed, it's just not correctly matched.
