Scrooge Error when defining Thrift exception

I noticed when a Thrift file defines an exception, scrooge throws an exception:

For example adding:

```
exception FooBar {
1: string code
}
```

to `test/src/main/scala/scalarules/test/twitter_scrooge/thrift/thrift2/thrift3/Thrift3.thrift` results in this:

```
ERROR: /absolute/path/to/test/src/main/scala/scalarules/test/twitter_scrooge/thrift/thrift2/thrift3/BUILD:4:1: Couldn't build file test/src/main/scala/scalarules/test/twitter_scrooge/thrift/thrift2/thrift3/thrift3_scrooge.jar: scala //test/src/main/scala/scalarules/test/twitter_scrooge/thrift/thrift2/thrift3:thrift3 failed (Exit 1)
bazel-out/darwin-fastbuild/bin/test/src/main/scala/scalarules/test/twitter_scrooge/thrift/thrift2/thrift3/tmp4446905357582031766/scalarules/test/twitter_scrooge/thrift/thrift2/thrift3/FooBar.scala:171: error: object finagle is not a member of package com.twitter
extends ThriftException with com.twitter.finagle.SourcedException with ThriftStruct
^
one error found
one error found
java.lang.RuntimeException: Build failed
at io.bazel.rulesscala.scalac.ScalacProcessor.compileScalaSources(ScalacProcessor.java:244)
at io.bazel.rulesscala.scalac.ScalacProcessor.processRequest(ScalacProcessor.java:69)
at io.bazel.rulesscala.worker.GenericWorker.runPersistentWorker(GenericWorker.java:45)
at io.bazel.rulesscala.worker.GenericWorker.run(GenericWorker.java:111)
at io.bazel.rulesscala.scalac.ScalaCInvoker.main(ScalaCInvoker.java:41)
```

Reproduce the failure by adding the FooBar exception to test/src/main/scala/scalarules/test/twitter_scrooge/thrift/thrift2/thrift3/Thrift3.thrift, then inspect the corresponding BUILD file and generated FooBar.scala. Determine why compilation requires com.twitter.finagle and verify that the example exception builds successfully without the reported error.

Written by the indexing model from the issue text.