SquishTests: Improve log messages of exceptions

...and make them more similar to Squish's own "Error" messages.

Change-Id: If5df701d4fa01fc1c1aea94cc9778a6a5dccc44e
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

tests/system/shared/fs_utils.py

@@ -30,7 +30,7 @@ def changeFilePermissions(dirPath, readPerm, writePerm, excludeFileNames=None):
             os.chmod(filePath, permission)
         except:
             t,v = sys.exc_info()[:2]
-            test.log("Error: %s(%s)" % (str(t), str(v)))
+            test.log("%s: %s" % (t.__name__, str(v)))
             result = False
     return result