Ensure watcher rethrows logger errors

[novemberborn]

The watcher would break if logger.finish() threw an exception. Instead rethrow this error (which causes the process to exit).

This surfaced in #1231 (comment).

[unional]

Tested and seems like it still hang the watch mode.

[novemberborn]

Strange, it works for me.

• Install npm i avajs/ava#rethrow-watch-logger-errors
• Modify node_modules/ava/lib/code-excerpt.js to const source = fs.readFileSync(file + 'foo', 'utf8');
• Write test file import test from 'ava'; test(t => { throw new Error("uhoh") })
• Run AVA: ./node_modules/.bin/ava --watch test.js

 ⠼ test › [anonymous]

  1 failed/private/var/folders/_6/p8qxp_3n62zg9081tvb0lcc80000gn/T/tmp.vx8nC52ks6/node_modules/ava/lib/watcher.js:15
		throw err;
		^

Error: ENOENT: no such file or directory, open '/private/var/folders/_6/p8qxp_3n62zg9081tvb0lcc80000gn/T/tmp.vx8nC52ks6/test.jsfoo'

[unional]

Async test
UPDATE: my test are async, I think that makes a difference here.

[novemberborn]

Even with import test from 'ava'; test(t => Promise.reject(new Error("uhoh"))) the watcher exits for me due to the reporter error.

[sindresorhus]

I can confirm it correctly crashes for me too when following the above steps.