3.6 compat

core/dbt/events/events.py

@@ -1,6 +1,5 @@
 
-from dataclasses import dataclass
-from typing import NoReturn, Union
+from typing import NamedTuple, NoReturn, Union
 
 
 # common trick for getting mypy to do exhaustiveness checks
@@ -9,16 +8,21 @@
 def assert_never(x: NoReturn) -> NoReturn:
     raise AssertionError("Unhandled type: {}".format(type(x).__name__))
 
+# The following classes represent the data necessary to describe a
+# particular event to both human readable logs, and machine reliable
+# event streams. The transformation to these forms will live in outside
+# functions.
+#
+# Until we drop support for Python 3.6 we must use NamedTuples over
+# frozen dataclasses.
 
 # TODO dummy class
-@dataclass(frozen=True)
-class OK:
+class OK(NamedTuple):
     result: int
 
 
 # TODO dummy class
-@dataclass(frozen=True)
-class Failure:
+class Failure(NamedTuple):
     msg: str