Determine why LESS import from /packages/ directory causes build error on Meteor 1.2 branch

[brylie]

When building the project after upgrading to Meteor 1.2, the following error appears in the terminal:

=> Errors prevented startup:                  

   While processing files with less (for target web.browser):
   client/style/global.less:3: Unknown import:
   /packages/bootstrap/bootstrap.import.less

   While processing files with less (for target web.cordova):
   client/style/global.less:3: Unknown import:
   /packages/bootstrap/bootstrap.import.less

Determine the cause of this error, including whether the import is necessary.

[brylie]

I have mentioned this issue in the Meteor Forums thread What's blocking you from updating to Meteor 1.2?