Avoid including DB details in exception messages

The keys are quite sufficient; we shouldn't be throwing passwords
around.

activerecord/lib/active_record/connection_adapters/connection_specification.rb

@@ -227,7 +227,7 @@ def resolve_symbol_connection(spec)
           if config = configurations[spec.to_s]
             resolve_connection(config)
           else
-            raise(AdapterNotSpecified, "'#{spec}' database is not configured. Available configuration: #{configurations.inspect}")
+            raise(AdapterNotSpecified, "'#{spec}' database is not configured. Available: #{configurations.keys.inspect}")
           end
         end