diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/ReviewerRecommender.java b/gerrit-server/src/main/java/com/google/gerrit/server/ReviewerRecommender.java
index d96c63c15a..5b3f093848 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/ReviewerRecommender.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/ReviewerRecommender.java
@@ -136,7 +136,7 @@ public class ReviewerRecommender {
                   .get()
                   .suggestReviewers(
                       projectState.getNameKey(),
-                      changeNotes.getChangeId(),
+                      changeNotes != null ? changeNotes.getChangeId() : null,
                       query,
                       reviewerScores.keySet()));
       String key = plugin.getPluginName() + "-" + plugin.getExportName();
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/ReviewerSuggestion.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/ReviewerSuggestion.java
index f64c9d04f0..198a5fde04 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/change/ReviewerSuggestion.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/ReviewerSuggestion.java
@@ -29,14 +29,15 @@ import java.util.Set;
 @ExtensionPoint
 public interface ReviewerSuggestion {
   /**
-   * Reviewer suggestion.
+   * Suggest reviewers to add to a change.
    *
    * @param project The name key of the project the suggestion is for.
-   * @param changeId The changeId that the suggestion is for. Can be an {@code null}.
-   * @param query The query as typed by the user. Can be an {@code null}.
+   * @param changeId The changeId that the suggestion is for. Can be {@code null}.
+   * @param query The query as typed by the user. Can be {@code null}.
    * @param candidates A set of candidates for the ranking. Can be empty.
-   * @return Set of suggested reviewers as a tuple of account id and score. The account ids listed
-   *     here don't have to be a part of candidates.
+   * @return Set of {@link SuggestedReviewer}s. The {@link
+   *     com.google.gerrit.reviewdb.client.Account.Id}s listed here don't have to be included in
+   *     {@code candidates}.
    */
   Set<SuggestedReviewer> suggestReviewers(
       Project.NameKey project,
diff --git a/tools/maven/mvn.py b/tools/maven/mvn.py
index f7b5aa82e9..a0939162a3 100755
--- a/tools/maven/mvn.py
+++ b/tools/maven/mvn.py
@@ -16,7 +16,7 @@
 from __future__ import print_function
 from optparse import OptionParser
 from os import path, environ
-from subprocess import check_output
+from subprocess import check_output, CalledProcessError
 from sys import stderr
 
 opts = OptionParser()
@@ -67,6 +67,8 @@ for spec in args.s:
   except Exception as e:
     print('%s command failed: %s\n%s' % (args.a, ' '.join(exe), e),
       file=stderr)
+    if environ.get('VERBOSE') and isinstance(e, CalledProcessError):
+      print('Command output\n%s' % e.output, file=stderr)
     exit(1)