Check connection string is set in rcdb cli 'db' command

python/rcdb/rcdb_cli/__main__.py

@@ -1,4 +1,3 @@
 from rcdb.rcdb_cli.app import rcdb_cli
 
 rcdb_cli(prog_name="rcdb")
-

python/rcdb/rcdb_cli/app.py

@@ -42,6 +42,9 @@ def rcdb_cli(ctx, user_config, connection, config, verbose):
     # Create a rcdb_app_context object and remember it as the context object.  From
     # this point onwards other commands can refer to it by using the
     # @pass_rcdb_context decorator.
+    if not connection:
+        print("(!)WARNING no connection provided! "
+              "Provide DB connection string via --connection/-c or RCDB_CONNECTION environment variable.")
     ctx.obj = RcdbApplicationContext(os.path.abspath(user_config), connection)
     ctx.obj.verbose = verbose
     for key, value in config:

python/rcdb/rcdb_cli/db.py

@@ -16,8 +16,16 @@ def db(ctx):
     """Database management commands."""
     if ctx.invoked_subcommand is None:
         connection_str = ctx.obj.connection_str
-        provider = RCDBProvider(connection_str, check_version=False)
-        schema_version, = provider.session.execute(select(SchemaVersion).order_by(SchemaVersion.version.desc())).first()
+
+        # We create provider manually and not using ctx.obj.db because we need check_version=False
+        # We separate class creation and connection because connection_str might be null
+        provider = RCDBProvider()
+        if not connection_str:
+            print("ERROR connection string is missing.")
+            exit(1)
+        provider.connect(connection_str, check_version=False)
+        query = select(SchemaVersion).order_by(SchemaVersion.version.desc())
+        schema_version, = provider.session.execute(query).first()
         print("Schema version: {} - '{}'".format(schema_version.version, schema_version.comment))