Fix(tensorboard): Check for executable to prevent crash

I replaced the direct import of `tensorflow` with a check for the `tensorboard` executable. This resolves the `illegal hardware instruction` crash that occurred on systems with CPUs lacking AVX2 support.

The new implementation ensures that the TensorBoard feature remains available if the `tensorboard` command is in the system's PATH, without causing a fatal error when the `tensorflow` library is incompatible with the underlying hardware.

kohya_gui/class_tensorboard.py

@@ -3,12 +3,15 @@ import gradio as gr
 import subprocess
 import time
 import webbrowser
+import shutil
 
 try:
-    os.environ["TF_ENABLE_ONEDNN_OPTS"] = "0"
-    import tensorflow  # Attempt to import tensorflow to check if it is installed
-
+    # os.environ["TF_ENABLE_ONEDNN_OPTS"] = "0"
+    # import tensorflow  # Attempt to import tensorflow to check if it is installed
+    if shutil.which("tensorboard"):
         visibility = True
+    else:
+        visibility = False
 except ImportError:
     visibility = False
 

tests/test_tensorboard_visibility.py

@@ -0,0 +1,20 @@
+import unittest
+from unittest.mock import patch
+import importlib
+
+class TestTensorboardVisibility(unittest.TestCase):
+
+    @patch('shutil.which', return_value='/usr/bin/tensorboard')
+    def test_tensorboard_visibility_when_tensorboard_is_present(self, mock_which):
+        import kohya_gui.class_tensorboard
+        importlib.reload(kohya_gui.class_tensorboard)
+        self.assertTrue(kohya_gui.class_tensorboard.visibility)
+
+    @patch('shutil.which', return_value=None)
+    def test_tensorboard_visibility_when_tensorboard_is_absent(self, mock_which):
+        import kohya_gui.class_tensorboard
+        importlib.reload(kohya_gui.class_tensorboard)
+        self.assertFalse(kohya_gui.class_tensorboard.visibility)
+
+if __name__ == '__main__':
+    unittest.main()