more exceptions?

app.py

@@ -21,11 +21,14 @@ description =  '''Explore hiding messages in images using content adaptive stega
 
 def HILL(input_image, operation, message, key):
     tmp_name = str(random.randint(100,500))
-    input_image.seek(0)
-    buffer = input_image.read()
-    I = cv2.imdecode(np.frombuffer(buffer, np.uint8), 1)
-    I = cv2.cvtColor(I,cv2.COLOR_BGR2GRAY)
-    cv2.imwrite('tmp/'+tmp_name+'.png',I)
+    try:
+        input_image.seek(0)
+        buffer = input_image.read()
+        I = cv2.imdecode(np.frombuffer(buffer, np.uint8), 1)
+        I = cv2.cvtColor(I,cv2.COLOR_BGR2GRAY)
+        cv2.imwrite('tmp/'+tmp_name+'.png',I)
+    except:
+        raise ValueError('Unable to read image')
 
     if operation == 'decode': 
         try: