Add LOG_LEVEL config key

.env.example

 # Example config file. Copy and customize this file to ".env". Don't commit ".env".
 
+LOG_LEVEL="INFO"
+
 # For production deployment, see http://flask.pocoo.org/docs/1.0/tutorial/deploy/#configure-the-secret-key
 SECRET_KEY="dev"
 

validata_ui/__init__.py

 import json
+import logging
 import os
 from pathlib import Path
 from urllib.parse import quote_plus
@@ -11,9 +12,10 @@ from cachetools.func import ttl_cache
 
 import opendataschema
 
-# Let this import after app initialisation
 from . import config
 
+log = logging.getLogger(__name__)
+
 
 @ttl_cache(maxsize=50, ttl=5*60)
 def download_with_cache(url):
@@ -28,6 +30,7 @@ def schema_from_url(url):
 # And load schema catalogs which urls are found in config.json
 schema_catalog_map = {}
 if config.HOMEPAGE_CONFIG:
+    log.info("Initializing homepage sections...")
     for section in config.HOMEPAGE_CONFIG['sections']:
         if isinstance(section['catalog'], str) and section['catalog'].startswith('http'):
             code = section['code']

validata_ui/config.py

 import json
 import logging
 import os
+import sys
 from pathlib import Path
 
 import requests
@@ -11,6 +12,15 @@ log = logging.getLogger(__name__)
 
 load_dotenv()
 
+LOG_LEVEL = os.environ.get("LOG_LEVEL", "INFO")
+numeric_log_level = getattr(logging, LOG_LEVEL.upper(), None)
+if not isinstance(numeric_log_level, int):
+    log.error('Invalid log level: {}'.format(LOG_LEVEL))
+logging.basicConfig(
+    format="%(levelname)s:%(name)s:%(message)s",
+    level=numeric_log_level,
+    stream=sys.stderr,  # script outputs data
+)
 
 SECRET_KEY = os.environ.get("SECRET_KEY") or None