Update app.py

app.py

@@ -1,3 +1,9 @@
+try:
+    import detectron2
+except:
+    import os
+    os.system('pip install git+https://github.com/facebookresearch/detectron2.git')
+
 from PIL import Image, ImageDraw
 import numpy as np
 import requests
@@ -113,3 +119,4 @@ gr.Interface(
     examples=[
             ["city1.jpg"],
         ]).launch()
+