Just unit test this instead

src/_zkapauthorizer/schema.py

@@ -132,9 +132,3 @@ _UPGRADES = {
         """,
     ],
 }
-
-def _check_consistency():
-    if _UPGRADES.keys() != range(len(_UPGRADES)):
-        raise TypeError("Inconsistent schema versions in schema upgraders.")
-
-_check_consistency()

src/_zkapauthorizer/tests/test_schema.py

+# coding: utf-8
+# Copyright 2019 PrivateStorage.io, LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Tests for ``_zkapauthorizer.schema``.
+"""
+
+from __future__ import (
+    absolute_import,
+)
+
+from testtools import (
+    TestCase,
+)
+from testtools.matchers import (
+    Equals,
+)
+
+from ..schema import (
+    _UPGRADES,
+)
+
+class UpgradeTests(TestCase):
+    def test_consistency(self):
+        """
+        Upgrades are defined for every version up to the latest version.
+        """
+        self.assertThat(
+            list(_UPGRADES.keys()),
+            Equals(list(range(len(_UPGRADES)))),
+        )