Only silence I18n deprecation warning if attr exists.

Fixes #1950.
[CHANGELOG] Update for #1950.
Merge branch 'master' of https://github.com/neonichu/CocoaPods into neonichu-master

Conflicts:
	CHANGELOG.md
Added changelog entry for pull #1960

Cleanup pod directory when download fails (probably due to a network error)
Merge pull request #1969 from alexrothenberg/patch-1

Added changelog entry for pull #1960