Reports only the first found error per failed task.

Error categories are sorted by priorities. If high level
error occur it might make the lower error categories
markers to appear in the log, so we need to skip them.

cwl_airflow/utilities/report.py

@@ -41,11 +41,11 @@ def get_error_category(context):
     retry, because the get_error_category function is called when the dag_run
     has failed, so all previous task retries didn't bring any positive results.
     We load logs only for the actually failed task, not for upstream_failed
-    tasks. All error categories should be mutullly exclusive so they are not
-    supposed to appear in the same log file all at once. We report only unique
-    error categories that's why we use set. The "Failed to run workflow step"
-    category additionally is filled with failed task ids. The returned value is
-    always a string.
+    tasks. All error categories are sorted by priority from higher level to the
+    lower one. We report only one (the highest, the first found) error category
+    per failed task. Error categories from all failed tasks are combined and
+    deduplicated. The "Failed to run workflow step" category additionally is
+    filled with failed task ids. The returned value is always a string.
     """
 
     ERROR_MARKERS = {
@@ -73,16 +73,16 @@ def get_error_category(context):
     for ti in failed_tis:
         ti.task = context["dag"].get_task(ti.task_id)                # for some reasons when retreived from DagRun we need to set "task" property from the DAG
         try:                                                         # in case log files were deleted or unavailable
-            logs, _ = log_handler.read(ti)                           # logs is always a list
-            for line in logs[-1].split("\n"):                        # first need to take the latest log and split it by "\n"
-                for marker, category in ERROR_MARKERS.items():
-                    if marker in line:
-                        categories.add(category)
+            logs, _ = log_handler.read(ti)                           # logs is always a list.
+            for marker, category in ERROR_MARKERS.items():
+                if marker in logs[-1]:                               # logs[-1] is a string with \n from the last task retry
+                    categories.add(category)
+                    break
         except Exception as err:
             logging.debug(f"Failed to define the error category for task {ti.task_id}. \n {err}")
 
     if categories:
-        return "\n".join(categories).format(", ".join( [ti.task_id for ti in failed_tis] ))  # mainly to fill in the placeholder with failed task ids
+        return ". ".join(categories).format(", ".join( [ti.task_id for ti in failed_tis] ))  # mainly to fill in the placeholder with failed task ids
     return "Unknown error. Contact support team"