Print error message if a package is skipped during DevFS sync. (#8960)
Print error message if a package is skipped during DevFS sync. (#8960)

* Print error message if a package is skipped during DevFS sync.

* review comments

* more review comments

* fix test

turnidge/flutter,flutter/flutter,flutter/flutter,flutter/flutter,flutter/flutter,flutter/flutter,tvolkert/flutter,cbracken/flutter,Hixie/flutter,cbracken/flutter,cbracken/flutter,cbracken/flutter,flutter/flutter,cbracken/flutter,tvolkert/flutter,Hixie/flutter,flutter/flutter,tvolkert/flutter,cbracken/flutter,cbracken/flutter,tvolkert/flutter,Hixie/flutter,Hixie/flutter,flutter/flutter,tvolkert/flutter,Hixie/flutter,tvolkert/flutter,Hixie/flutter,Hixie/flutter,turnidge/flutter,tvolkert/flutter,Hixie/flutter,tvolkert/flutter,tvolkert/flutter,Hixie/flutter,flutter/flutter,flutter/flutter,cbracken/flutter,turnidge/flutter,turnidge/flutter,Hixie/flutter,tvolkert/flutter,cbracken/flutter,cbracken/flutter,turnidge/flutter