Traceback (most recent call last):
  File "/var/tmp/portage/dev-python/rdflib-4.2.2/work/rdflib-4.2.2-python3_7/build/src/rdflib/plugins/sparql/evaluate.py", line 330, in evalSlice
    next(res)
StopIteration

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/lib/python3.7/site-packages/nose/case.py", line 197, in runTest
    self.test(*self.arg)
  File "/var/tmp/portage/dev-python/rdflib-4.2.2/work/rdflib-4.2.2-python3_7/build/src/test/test_dawg.py", line 434, in query_test
    set(res2)
  File "/var/tmp/portage/dev-python/rdflib-4.2.2/work/rdflib-4.2.2-python3_7/build/src/rdflib/query.py", line 258, in __iter__
    for b in self._genbindings:
RuntimeError: generator raised StopIteration

Patch backported from
https://github.com/RDFLib/rdflib/commit/58c45d6f30af88a22f60edcb9a459648a885e226

--- a/rdflib/plugins/sparql/evaluate.py
+++ b/rdflib/plugins/sparql/evaluate.py
@@ -15,6 +15,7 @@
 """
 
 import collections
+import itertools
 
 from rdflib import Variable, Graph, BNode, URIRef, Literal
 
@@ -323,22 +324,9 @@
 
 
 def evalSlice(ctx, slice):
-    # import pdb; pdb.set_trace()
     res = evalPart(ctx, slice.p)
-    i = 0
-    while i < slice.start:
-        res.next()
-        i += 1
-    i = 0
-    for x in res:
-        i += 1
-        if slice.length is None:
-            yield x
-        else:
-            if i <= slice.length:
-                yield x
-            else:
-                break
+
+    return itertools.islice(res, slice.start, slice.start+slice.length if slice.length is not None else None)
 
 
 def evalReduced(ctx, part):
--- a/rdflib/query.py
+++ b/rdflib/query.py
@@ -1,5 +1,6 @@
 
 import os
+import itertools
 import shutil
 import tempfile
 import warnings
@@ -181,7 +182,7 @@
         return self._bindings
 
     def _set_bindings(self, b):
-        if isinstance(b, types.GeneratorType):
+        if isinstance(b, (types.GeneratorType, itertools.islice)):
             self._genbindings = b
             self._bindings = []
         else: