correct filter events on the migration event horizon

events that existed *prior* to the partition migration will have
`job_created=1970-01-01` auto-applied at migration time; as such,
queries for these events e.g., /api/v2/job/N/job_events/
use 1970-01-01 in related event searche

events created *after* the partition migration (net-new playbook runs
will have `job_created` values that *exactly match* the related
`UnifiedJob.created` field.

awx/main/utils/common.py

@@ -90,7 +90,7 @@ __all__ = [
     'create_temporary_fifo',
     'truncate_stdout',
     'deepmerge',
-    'cleanup_new_process',
+    'get_event_partition_epoch',
 ]
 
 
@@ -208,6 +208,28 @@ def memoize_delete(function_name):
     return cache.delete(function_name)
 
 
+@memoize(ttl=3600 * 24)  # in practice, we only need this to load once at process startup time
+def get_event_partition_epoch():
+    from django.db.migrations.recorder import MigrationRecorder
+    return MigrationRecorder.Migration.objects.filter(
+        app='main', name='0124_event_partitions'
+    ).first().applied
+
+
+@memoize()
+def get_ansible_version():
+    """
+    Return Ansible version installed.
+    Ansible path needs to be provided to account for custom virtual environments
+    """
+    try:
+        proc = subprocess.Popen(['ansible', '--version'], stdout=subprocess.PIPE)
+        result = smart_str(proc.communicate()[0])
+        return result.split('\n')[0].replace('ansible', '').strip()
+    except Exception:
+        return 'unknown'
+
+
 def get_awx_version():
     """
     Return AWX version as reported by setuptools.