Update MULTIMODAL initialization to use environment variable and improve error message

app.py

@@ -5,14 +5,14 @@ import os
 from distutils.util import strtobool
 
 
-MULTIMODAL = False
+MULTIMODAL = os.environ.get("MULTIMODAL", "false")
 
 # 1) convert common truthy/falsy strings to bool
 try:
     MULTIMODAL = bool(strtobool(MULTIMODAL))
 except ValueError:
     # catch unrecognized values
-    raise ValueError(f"Invalid MULTIMODAL value: {MULTIMODAL!r}. Use true/false, 1/0, yes/no.")
+    raise ValueError(f"Invalid MULTIMODAL value: Use true/false, 1/0, yes/no.")
 
 AUTHS = [(os.environ.get('USER'), os.environ.get('PW'))]