Get rid of custom ExceptionRule methods

The only remaining methods on ExceptionRule after this are methods that
also exist on ExpectedException, which will allow us to, in the next CL,
swap out the one for the other and then run the automated refactoring to
turn it all into assertThrows/expectThrows.

Note that there were some assertions about root causes that couldn't
easily be turned into ExpectedException invocations, so I simply
converted them directly to usages of assertThrows/expectThrows.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=178623431

javatests/google/registry/testing/ExceptionRule.java

@@ -16,7 +16,6 @@ package google.registry.testing;
 
 import static com.google.common.base.Preconditions.checkState;
 import static com.google.common.base.Strings.nullToEmpty;
-import static com.google.common.base.Throwables.getRootCause;
 import static google.registry.testing.EppExceptionSubject.assertAboutEppExceptions;
 
 import google.registry.flows.EppException;
@@ -37,8 +36,6 @@ public class ExceptionRule implements TestRule {
   @Nullable
   String expectedMessage;
 
-  private boolean useRootCause;
-
   @Override
   public Statement apply(final Statement base, Description description) {
     return new Statement() {
@@ -53,10 +50,9 @@ public class ExceptionRule implements TestRule {
                 expectedMessage == null ? "" : (" with message: " + expectedMessage)));
           }
         } catch (Throwable e) {
-          Throwable cause = useRootCause ? getRootCause(e) : e;
           if (expectedExceptionClass == null
-              || !(expectedExceptionClass.isAssignableFrom(cause.getClass())
-                  && nullToEmpty(cause.getMessage()).contains(nullToEmpty(expectedMessage)))) {
+              || !(expectedExceptionClass.isAssignableFrom(e.getClass())
+                  && nullToEmpty(e.getMessage()).contains(nullToEmpty(expectedMessage)))) {
             throw e;  // We didn't expect this so pass it through.
           }
           if (e instanceof EppException) {
@@ -72,19 +68,7 @@ public class ExceptionRule implements TestRule {
     this.expectedExceptionClass = expectedExceptionClass;
   }
 
-  public void expect(Class<? extends Throwable> expectedExceptionClass, String expectedMessage) {
-    expect(expectedExceptionClass);
+  public void expectMessage(String expectedMessage) {
     this.expectedMessage = expectedMessage;
   }
-
-  public void expectRootCause(Class<? extends Throwable> expectedExceptionClass) {
-    expect(expectedExceptionClass);
-    this.useRootCause = true;
-  }
-
-  public void expectRootCause(
-      Class<? extends Throwable> expectedExceptionClass, String expectedMessage) {
-    expect(expectedExceptionClass, expectedMessage);
-    this.useRootCause = true;
-  }
 }