Catch ImportError when awscrt is not installed

Author: jonathan343

packages/smithy-aws-core/src/smithy_aws_core/interceptors/user_agent.py

@@ -68,5 +68,5 @@ def _crt_version(self) -> list[UserAgentComponent]:
             import awscrt
 
             return [UserAgentComponent("md", "awscrt", awscrt.__version__)]
-        except AttributeError:
+        except (ImportError, AttributeError):
             return []