Pin jupyter transitive deps in integration tests (#6568)

### Problem

As described in pex-tool/pex#561, jupyter's transitive deps float. Today that caused breakage.

### Solution

Pin the relevant deps (ht John in pex-tool/pex#562).

testprojects/src/python/interpreter_selection/resolver_blacklist_testing/BUILD

@@ -7,13 +7,17 @@ python_binary(
   ]
 )
 
-# Without blacklisting, pex resolver will error out
-# on a transitive requirement of jupyter (functools32)
-# when resolving for Python 3.
+# This library requires pex blacklisting under python 3, because the pex resolver will error out
+# on a transitive requirement of jupyter (functools32).
+#
+# This test also runs under python 2 though, and so in order to avoid dep floats of jupyter's
+# transitive deps (which can float upward to versions that do not support python 2), we pin them.
 python_requirement_library(
   name='reqlib',
   requirements=[
-    python_requirement('jupyter'),
+    python_requirement('jupyter==1.0.0'),
+    python_requirement('ipykernel<5'),
+    python_requirement('ipython<6'),
   ]
 )