diff --git a/tests/pipeline/test_engine.py b/tests/pipeline/test_engine.py
index fecebd93..e656cbae 100644
--- a/tests/pipeline/test_engine.py
+++ b/tests/pipeline/test_engine.py
@@ -228,7 +228,7 @@ class ConstantInputTestCase(WithTradingEnvironment, ZiplineTestCase):
 
         # We shouldn't be able to compute dates[8], since we only know about 8
         # prior dates, and we need a window length of 10.
-        with self.assertRaises(NoFurtherDataError) as e:
+        with self.assertRaises(NoFurtherDataError):
             engine.run_pipeline(p, self.dates[8], self.dates[8])
 
     def test_input_dates_provided_by_default(self):
@@ -255,7 +255,6 @@ class ConstantInputTestCase(WithTradingEnvironment, ZiplineTestCase):
         column = results.unstack().iloc[:, 0].values
         check_arrays(column, self.dates[:2].values)
 
-
     def test_same_day_pipeline(self):
         loader = self.loader
         engine = SimplePipelineEngine(
diff --git a/tests/pipeline/test_factor.py b/tests/pipeline/test_factor.py
index ba50fdae..91acbe35 100644
--- a/tests/pipeline/test_factor.py
+++ b/tests/pipeline/test_factor.py
@@ -26,7 +26,7 @@ from zipline.errors import UnknownRankMethod
 from zipline.lib.labelarray import LabelArray
 from zipline.lib.rank import masked_rankdata_2d
 from zipline.lib.normalize import naive_grouped_rowwise_apply as grouped_apply
-from zipline.pipeline import Classifier, Factor, Filter, TermGraph
+from zipline.pipeline import Classifier, Factor, Filter
 from zipline.pipeline.factors import (
     Returns,
     RSI,
@@ -37,7 +37,6 @@ from zipline.testing import (
     parameter_space,
     permute_rows,
 )
-from zipline.utils.functional import dzip_exact
 from zipline.utils.numpy_utils import (
     categorical_dtype,
     datetime64ns_dtype,
diff --git a/tests/pipeline/test_filter.py b/tests/pipeline/test_filter.py
index 958c6e90..62cc187d 100644
--- a/tests/pipeline/test_filter.py
+++ b/tests/pipeline/test_filter.py
@@ -26,11 +26,11 @@ from numpy import (
 from numpy.random import randn, seed as random_seed
 
 from zipline.errors import BadPercentileBounds
-from zipline.pipeline import Filter, Factor, TermGraph
+from zipline.pipeline import Filter, Factor
 from zipline.pipeline.classifiers import Classifier
 from zipline.pipeline.factors import CustomFactor
 from zipline.pipeline.filters import All, Any, AtLeastN
-from zipline.testing import check_arrays, parameter_space, permute_rows
+from zipline.testing import parameter_space, permute_rows
 from zipline.utils.numpy_utils import float64_dtype, int64_dtype
 from .base import BasePipelineTestCase, with_default_shape
 
diff --git a/zipline/pipeline/graph.py b/zipline/pipeline/graph.py
index eedb8c3c..e18c3602 100644
--- a/zipline/pipeline/graph.py
+++ b/zipline/pipeline/graph.py
@@ -5,7 +5,7 @@ from networkx import (
     DiGraph,
     topological_sort,
 )
-from six import iteritems
+from six import iteritems, itervalues
 from zipline.utils.memoize import lazyval
 from zipline.pipeline.visualize import display_graph
 
@@ -48,7 +48,7 @@ class TermGraph(DiGraph):
 
         self._frozen = False
         parents = set()
-        for name, term in iteritems(terms):
+        for term in itervalues(terms):
             self._add_to_graph(term, parents)
             # No parents should be left between top-level terms.
             assert not parents