The pub package manager is a complex tool with many functionalities, so it is not surprising that occasionally something goes wrong. The
pub get command downloads all the libraries needed by your app, as specified in the
pubspec.yaml file. Running
pub get behind a proxy or firewall used to be a problem, but it was solved in the majority of cases. If this still haunts you, look at the corresponding section at https://www.dartlang.org/tools/editor/troubleshoot.html.
This recipe is especially useful when you encounter the following error in your Dart console while trying to open a project in Dart Editor during the pub get phase:
Pub install fails with 'Deletion failed'
First try this; ...