[iso-core] Fix imap error detection!

Summary:
We were only detecting and classifying IMAP errors as retryable and non
retryable in a few places, but errors thrown in any of our imap
operations were not being properly passed through our `convertImapErrors` :(

This was broken, oh so broken

Also loosen condition to detect System Errors

Test Plan: manual

Reviewers: spang, mark, evan

Reviewed By: evan

Differential Revision: https://phab.nylas.com/D4022

packages/isomorphic-core/src/imap-connection.es6

@@ -346,7 +346,11 @@ class IMAPConnection extends EventEmitter {
         clearTimeout(socketTimeout)
         resolve(...args)
       }
-      return callback(cbResolve, reject)
+      const cbReject = (error) => {
+        clearTimeout(socketTimeout)
+        reject(convertImapError(error))
+      }
+      return callback(cbResolve, cbReject)
     })
     .finally(() => {
       if (this._imap) {

packages/isomorphic-core/src/imap-errors.js

@@ -82,7 +82,7 @@ function convertImapError(imapError) {
     error.source = imapError.source
     return error
   }
-  if (imapError.message.includes('System Error')) {
+  if (/system error/i.test(imapError.message)) {
     // System Errors encountered in the wild so far have been retryable.
     error = new RetryableError(imapError)
     error.source = imapError.source