See technique used in `fast-syntax-highlighting`:
- ca2e18bbc9
- http://www.zsh.org/mla/users/2018/msg00424.html

Only a problem in synchronous mode

`stty` occasionally hangs (always in CircleCI) inside the async pty.

Disable the tests for now until we can figure out and fix/workaround
this issue.

For unknown reasons, the pty will occasionally quit running. In these
cases, we still want to remove it so that a fresh one can be created. We
don't actually need this check because error messages from `zle` and
`zpty` are redirected to /dev/null.

One sure way to kill all currently running pty's is to run `exit` in a
subshell. Even without zsh-autosuggestions loaded, the following works:

    % zmodload zsh/zpty
    % zpty -b foo cat
    % zpty -b bar cat
    % zpty
    (31689) bar: cat
    (31666) foo: cat
    % $(exit)
    % zpty
    (finished) bar: cat
    (finished) foo: cat

Issue #188. PR #324.

Thanks to @toadjaune and @IngoHeimbach.

Specific case where this matters is following:

Be in vi insert mode with some text in the buffer and the cursor at the
end of the buffer. Press `esc` to trigger `vi-cmd-mode widget`, then
before the cursor moves (KEYTIMEOUT), press `h` to trigger
`vi-backward-char` widget. When `vi-cmd-mode` original widget exits,
KEYS_QUEUED_COUNT will be non-zero and the suggestion will be lost.

Useful with `binding.pry` to inspect behavior of tests.

These widgets rely on `$LASTWIDGET` being set to restore the cursor
position. When asynchronous suggestions are enabled, and the widget
triggers a suggestion to be fetched, `autosuggest-suggest` will be
called and $LASTWIDGET will be set to it.

This fixes a small issue in src/widgets.zsh which makes it so if you
alias [ to g[ (as is done in prezto if the gnu-utility module is loaded)
autosuggestions would fail.

The documentation for GNU test mentions that -o and -a should be avoided
if possible because it's not very clear. Also, with zsh and [[ -o
actually tests if an option is set, which makes this option even more
confusing.

Seems like this would happen on some machines but not on others. Not
sure exactly what's going on, but this is such an edge case I'm just
going to remove the test.

Github #247 and #258

While they are still experimental

[GitHub #219]

Intended to be helpful for folks using bracketed-paste-magic and other
widgets that use `zle -U`.

Depends on patch to ZSH from workers/40702:

  http://www.zsh.org/mla/workers/2017/msg00414.html

Puts in a better fix for #126 and related issues.

Can attach while tests are stopped with `tmux -L <socket_name> attach`

Fixes flaky test

Prevents some flakiness in tests

As far as I know, `fc` makes it impossible to tell whether history items
used an actual newline character or the string "\n". Pulling from the
`$history` array gives a more accurate representation of the actual
command that was run.