Include --trace to debug some travis-ci problems.
Include --trace to debug some travis-ci problems.

gaapt/bookyt,wtag/bookyt,silvermind/bookyt,xuewenfei/bookyt,wtag/bookyt,gaapt/bookyt,huerlisi/bookyt,hauledev/bookyt,hauledev/bookyt,huerlisi/bookyt,wtag/bookyt,gaapt/bookyt,silvermind/bookyt,silvermind/bookyt,hauledev/bookyt,huerlisi/bookyt,gaapt/bookyt,hauledev/bookyt,silvermind/bookyt,xuewenfei/bookyt,xuewenfei/bookyt