Send an email when an update fails

[jimaek]

For example chartist changed their structure and libgrabber stopped updating it. The only way to see the problem is to read the logs

info: Updating chartist.js to v0.4.3
info: Copied 0 files name=chartist.js, version=v0.4.3, files=[]
warn: Something might be wrong with update.json name=chartist.js, version=v0.4.3

an other example

error: Error in reading metadata file /home/jsdelivr/files/underscore.string/update.json
warn: Failed to read metadata metadataPath=/home/jsdelivr/files/underscore.string/update.json,
error: Failed to update project /home/jsdelivr/files/underscore.string/update.json
error: Failed to update project

There needs to be a way to automatically notify the admin via email about a library that fails to update