.setMessage("Non-parseable POM " + modelSource.getLocation() + ": " + e.getMessage())
                    .setException(e));
            throw problems.newModelBuildingException();
        } catch (IOException e) {
            String msg = e.getMessage();
            if (msg == null || msg.isEmpty()) {

            buffer.append(" for ").append(sourceHint);
        }

        buffer.append(' ').append(message);

        problems.add(new ModelProblemCollectorRequest(severity, version)
                .setMessage(buffer.toString())
                .setLocation(getLocation(fieldName, tracker)));
    }

    private static org.apache.maven.model.InputLocation getLocation(String fieldName, InputLocationTracker tracker) {

                    ModelProblem.Version.BASE,
                    "Non-parseable POM " + modelSource.getLocation() + ": " + e.getMessage(),
                    e);
            throw problems.newModelBuilderException();
        } catch (IOException e) {
            String msg = e.getMessage();
            if (msg == null || msg.isEmpty()) {

                        if (result == null || result.getEffectiveModel() == null) {
                            throw new ProjectBuildingException(
                                    e.getModelId(), e.getMessage(), pomFile != null ? pomFile.toFile() : null, e);
                        }
                        // validation error, continue project building and delay failing to help IDEs
                        error = e;

        OperationDescriptor parent = getParentDescriptor(descriptor.getParentId());
        Destination destination = Destination.fromCode(event.getResult().getDestination());
        String message = event.getResult().getMessage();
        return new DefaultTestOutputOperationDescriptor(descriptor, parent, destination, message);
    }

    private static FailureContainer toFailureContainer(@Nullable InternalBasicProblemDetails problemDetails) {

                        assert it instanceof UnresolvedDependencyResult
                        assert it.requested.toString() == 'org:leaf:(,1.0)'
                        assert it.failure.getMessage().startsWith('Could not find any version that matches org:leaf:(,1.0).')
                    }
                    b.dependencies.each {
                        assert it instanceof ResolvedDependencyResult

      } catch (Exception | StackOverflowError e) {
        // Any Exception is either a RuntimeException or sneaky checked exception.
        //
        // Don't call getMessage or toString() on the exception, in case the exception thrown by the
        // subclass is implemented with bugs similar to the subclass.
        pendingDescription = "Exception thrown from implementation: " + e.getClass();

      } catch (Exception | StackOverflowError e) {
        // Any Exception is either a RuntimeException or sneaky checked exception.
        //
        // Don't call getMessage or toString() on the exception, in case the exception thrown by the
        // subclass is implemented with bugs similar to the subclass.
        pendingDescription = "Exception thrown from implementation: " + e.getClass();

      Map<Integer, String> unused =
          Maps.uniqueIndex(ImmutableSet.of("one", "uno"), Functions.constant(1));
      fail();
    } catch (IllegalArgumentException expected) {
      assertThat(expected.getMessage()).contains("Multimaps.index");
    }
  }

  /** Null values are not allowed. */
  public void testUniqueIndexNullValue() {
    List<@Nullable String> listWithNull = Lists.newArrayList((String) null);