* fix(exec): consistent error message for maxBuffer
This explicitly checks for maxBuffer errors in exec-child.js and
provides a consistent error message. This modifies the test to verify
this.
This also supports the change in Node v10, which emits this as a
RangeError instead of a regular Error.
Although the error message is now explicit, this is not part of our API,
since it's just tacked onto the end of exec's stderr.
Fixes#915
* Remove debugging log, ignore uncovered lines
e606706855