Removed reliance on Python 3.6's AbstractContextManager

iris/raw.py

@@ -5,7 +5,6 @@
 """
 from abc import abstractmethod
 from collections import OrderedDict
-from contextlib import AbstractContextManager
 from functools import partial
 
 import numpy as np
@@ -15,7 +14,7 @@
 
 from .meta import ExperimentalParameter, MetaRawDataset
 
-class AbstractRawDataset(AbstractContextManager, metaclass = MetaRawDataset):
+class AbstractRawDataset(object, metaclass = MetaRawDataset):
     """
     Abstract base class for ultrafast electron diffraction data set. 
     RawDatasetBase allows for enforced metadata types and values, 
@@ -78,6 +77,9 @@ def __init__(self, source = None, metadata = dict()):
         if metadata:
             self.update_metadata(metadata)
 
+    def __enter__(self):
+        return self
+
     def __exit__(self, *exc):
         pass