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Change-Id: I211d2674cfd4f9480a373f5d2d8d9c2abca266e9
enforce findbugs 2.0.3.

Since Gradle 2.1 findbugs now defaults to 3.0.0 which is
not compatible with Java6

Change-Id: I790350701be581cf1800f312eff1d4d4cbd8688b