Error codes improvement

[carlosmorasalguero]

Hi, i noticed the error codes could be improved a little bit.

1: INVALID_URL_ERR // unable to connect to host
2: CONNECTION_ERR // able to connect to host, but unable to download the zip
3: UNZIP_ERR // unable to unzip the zip

For 1: INVALID_URL_ERR // unable to connect to host
the code says invalid url, but the error really means unable to connect to the host, could be due to lack for internet connectivity (device not online), or DNS error... i would suggest a change to have 1: UNABLE_TO_CONNECT