第一个错误
<pre>
Error:Execution failed for task ':litecashier:compilePoslabReleaseJavaWithJavac'.

When running gradle with java 5, 6 or 7, you must set the path to jdk8, either with property retrolambda.jdk or environment variable JAVA8_HOME
</pre>

第二个错误
<pre>
UNEXPECTED TOP-LEVEL EXCEPTION:
Error:com.android.dx.cf.iface.ParseException: bad class file magic (cafebabe) or version (0034.0000)
at com.android.dx.cf.direct.DirectClassFile.parse0(DirectClassFile.java:472)
at com.android.dx.cf.direct.DirectClassFile.parse(DirectClassFile.java:406)
at com.android.dx.cf.direct.DirectClassFile.parseToInterfacesIfNecessary(DirectClassFile.java:388)
at com.android.dx.cf.direct.DirectClassFile.getMagic(DirectClassFile.java:251)
at com.android.dx.command.dexer.Main.parseClass(Main.java:764)
at com.android.dx.command.dexer.Main.access$1500(Main.java:85)
at com.android.dx.command.dexer.Main$ClassParserTask.call(Main.java:1684)
at com.android.dx.command.dexer.Main.processClass(Main.java:749)
... 12 more
2 errors; aborting
Error:Execution failed for task ':litecashier:transformClassesWithDexForPoslabRelease'.

com.android.build.api.transform.TransformException: com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command '/Library/Java/JavaVirtualMachines/jdk1.8.0_73.jdk/Contents/Home/bin/java'' finished with non-zero exit value 1
</pre>

参考文章

1. RxJava 与 Retrofit 结合的最佳实践