Split execution module in submodules for better readability.

tests/io/test_csv.py

@@ -2,7 +2,7 @@ import pytest
 
 from bonobo import Bag, CsvReader, CsvWriter
 from bonobo.constants import BEGIN, END
-from bonobo.execution import NodeExecutionContext
+from bonobo.execution.node import NodeExecutionContext
 from bonobo.util.testing import CapturingNodeExecutionContext
 
 

tests/io/test_file.py

@@ -2,7 +2,7 @@ import pytest
 
 from bonobo import Bag, FileReader, FileWriter
 from bonobo.constants import BEGIN, END
-from bonobo.execution import NodeExecutionContext
+from bonobo.execution.node import NodeExecutionContext
 from bonobo.util.testing import CapturingNodeExecutionContext
 
 

tests/io/test_json.py

@@ -2,7 +2,7 @@ import pytest
 
 from bonobo import Bag, JsonReader, JsonWriter
 from bonobo.constants import BEGIN, END
-from bonobo.execution import NodeExecutionContext
+from bonobo.execution.node import NodeExecutionContext
 from bonobo.util.testing import CapturingNodeExecutionContext
 
 

tests/test_execution.py

@@ -1,7 +1,7 @@
 from bonobo import Graph, NaiveStrategy, Bag
 from bonobo.config.processors import contextual
 from bonobo.constants import BEGIN, END
-from bonobo.execution import GraphExecutionContext
+from bonobo.execution.graph import GraphExecutionContext
 
 
 def generate_integers():