chore: Re-enable error for when DATABASE_URL is missing

config/runtime.exs

@@ -23,12 +23,10 @@ end
 if config_env() == :prod do
   database_url =
     System.get_env("DATABASE_URL") ||
-      IO.puts("Warning: Environment variable DATABASE_URL is missing.")
-
-  # raise """
-  # environment variable DATABASE_URL is missing.
-  # For example: ecto://USER:PASS@HOST/DATABASE
-  # """
+      raise """
+      environment variable DATABASE_URL is missing.
+      For example: ecto://USER:PASS@HOST/DATABASE
+      """
 
   # maybe_ipv6 = if System.get_env("ECTO_IPV6") in ~w(true 1), do: [:inet6], else: []