Add custom format for warnings (#477)

[cellxgene] Warning: <message>

server/app/app.py

@@ -1,4 +1,5 @@
 import os
+import warnings
 
 from flask import Flask
 from flask_caching import Cache
@@ -7,11 +8,13 @@ from flask_cors import CORS
 from flask_restful_swagger_2 import get_swagger_blueprint
 
 from .rest_api.rest import get_api_resources
-from .util.utils import Float32JSONEncoder
+from .util.utils import Float32JSONEncoder, custom_format_warning
 from .web import webapp
 
 REACTIVE_LIMIT = 1_000_000
 
+warnings.formatwarning = custom_format_warning
+
 app = Flask(__name__, static_folder="web/static")
 app.json_encoder = Float32JSONEncoder
 cache = Cache(app, config={"CACHE_TYPE": "simple", "CACHE_DEFAULT_TIMEOUT": 860000})