Simplify case_dictionary

dockerfiles/ci-tools/report_diff.py

@@ -6,12 +6,11 @@ from junitparser import JUnitXml, TestSuite
 
 
 def case_dictionary(report):
-    result = {}
-    for suite in report:
-        for case in suite:
-            key = (case.classname, case.name)
-            result[key] = case
-    return result
+    return {
+        (case.classname, case.name): case
+        for suite in report
+        for case in suite
+    }
 
 
 def compare_reports(path_before, path_after, path_out):