Fix tests for new tensorboard >= 2.6 (#8789)

(cherry picked from commit 346cef2)

Author: awaelchli

tests/loggers/test_tensorboard.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
+import operator
 import os
 from argparse import Namespace
 from unittest import mock
@@ -20,14 +21,19 @@
 import torch
 import yaml
 from omegaconf import OmegaConf
-from tensorboard.backend.event_processing.event_accumulator import EventAccumulator
 
 from pytorch_lightning import Trainer
 from pytorch_lightning.loggers import TensorBoardLogger
+from pytorch_lightning.utilities.imports import _compare_version
 from tests.helpers import BoringModel
 
 
+@pytest.mark.skipif(
+    _compare_version("tensorboard", operator.ge, "2.6.0"), reason="cannot import EventAccumulator in >= 2.6.0"
+)
 def test_tensorboard_hparams_reload(tmpdir):
+    from tensorboard.backend.event_processing.event_accumulator import EventAccumulator
+
     class CustomModel(BoringModel):
         def __init__(self, b1=0.5, b2=0.999):
             super().__init__()