Looks like there are binary incompatible changes when upgrading from 1.7.0 to 1.7.1.
java.lang.NoSuchMethodError: org.assertj.core.api.Assertions.assertThat(I)Lorg/assertj/core/api/IntegerAssert;
at org.assertj.android.api.view.AbstractViewAssert.isGone(AbstractViewAssert.java:773)
...
Looks like there are binary incompatible changes when upgrading from 1.7.0 to 1.7.1.