Resolve TypeError during FuzzContext creation

In the creation of a FuzzContext object, 'issue_metadata' in 'fuzzer_metadata' must be a string, not a dictionary.

Author: AashutoshMurthy

src/clusterfuzz/_internal/bot/tasks/utasks/fuzz_task.py

@@ -16,6 +16,7 @@
 import collections
 import datetime
 import itertools
+import json
 import os
 import random
 import re
@@ -1154,6 +1155,10 @@ def key_fn(crash):
                 f'{group.crashes[0].crash_state}')
       continue
 
+    if 'issue_metadata' in context.fuzzer_metadata:
+      context.fuzzer_metadata['issue_metadata'] = json.dumps(
+          context.fuzzer_metadata['issue_metadata'])
+
     group_proto = uworker_msg_pb2.FuzzTaskCrashGroup(
         context=uworker_msg_pb2.FuzzContext(
             redzone=context.redzone,

src/clusterfuzz/_internal/tests/core/bot/tasks/utasks/fuzz_task_test.py

@@ -778,7 +778,7 @@ def test_existing_unreproducible_testcase(self):
             crash_revision=crash_revision,
             fuzzer_name='fuzzer',
             window_argument='win_args',
-            fuzzer_metadata={},
+            fuzzer_metadata={'issue_metadata': {}},
             testcases_metadata={},
             timeout_multiplier=1,
             test_timeout=2,
@@ -851,7 +851,7 @@ def test_create_many_groups(self, project_name):
             crash_revision=1234,
             fuzzer_name='fuzzer',
             window_argument='win_args',
-            fuzzer_metadata={},
+            fuzzer_metadata={'issue_metadata': {}},
             testcases_metadata={},
             timeout_multiplier=1,
             test_timeout=2,