properly raise TypeError and rephrase error message.

workflow/Snakefile

@@ -57,7 +57,8 @@ try:
         rule_config = yaml.safe_load(_file)
     logger.info(f"Loaded rule_config from {config['optional']['rule_config']}.")
 except TypeError:
-    logger.error(f'No string supplied at field "rule_config", but: {config["optional"]["rule_config"]}')
+    logger.error(f'No string supplied at field "rule_config", but: {type(config["optional"]["rule_config"])} with content: {config["optional"]["rule_config"]}')
+    raise
 except FileNotFoundError:
     logger.error(f"No rule config file found at {config['optional']['rule_config']}. Either provide file or remove rule_config parameter from config.yaml! ")
     raise