Add workaround for using pip 10.0 "internal" API in upgrades view

tailbone/views/upgrades.py

@@ -31,10 +31,18 @@ import re
 import logging
 
 import six
-from pip.download import PipSession
-from pip.req import parse_requirements
 from sqlalchemy import orm
 
+# TODO: pip has declared these to be "not public API" so we should find another way..
+try:
+    # this works for now, with pip 10.0.1
+    from pip._internal.download import PipSession
+    from pip._internal.req import parse_requirements
+except ImportError:
+    # this should work with pip < 10.0
+    from pip.download import PipSession
+    from pip.req import parse_requirements
+
 from rattail.db import model, Session as RattailSession
 from rattail.time import make_utc
 from rattail.threads import Thread