Update app.py

app.py

@@ -1,8 +1,9 @@
-try:
-    import detectron2
-except:
-    import os 
-    os.system('pip install git+https://github.com/facebookresearch/detectron2.git')
+# workaround: install old version of pytorch since detectron2 hasn't released packages for pytorch 1.9 (issue: https://github.com/facebookresearch/detectron2/issues/3158)
+os.system('pip install torch==1.8.0+cu101 torchvision==0.9.0+cu101 -f https://download.pytorch.org/whl/torch_stable.html')
+
+# install detectron2 that matches pytorch 1.8
+# See https://detectron2.readthedocs.io/tutorials/install.html for instructions
+os.system('pip install -q detectron2 -f https://dl.fbaipublicfiles.com/detectron2/wheels/cu101/torch1.8/index.html')
     
 import os
 import gradio as gr