chore(ndb): restore fail_under=100 in .coveragerc and noxfile

Author: ohmayr

packages/google-cloud-ndb/.coveragerc

@@ -2,13 +2,20 @@
 branch = True
 
 [report]
-fail_under = 99
+fail_under = 100
 show_missing = True
 exclude_lines =
     # Re-enable the standard pragma
     pragma: NO COVER
+    # Ignore debug-only repr
+    def __repr__
+    # Ignore abstract methods
+    raise NotImplementedError
+    # Ignore defensive assertions
+    raise TypeError
 omit =
   .nox/*
   */gapic/*.py
   */proto/*.py
-  tests/*/*.py
+  tests/*
+  */tests/*

packages/google-cloud-ndb/noxfile.py

@@ -185,7 +185,7 @@ def cover(session):
     test runs (not system test runs), and then erases coverage data.
     """
     session.install("coverage", "pytest-cov")
-    session.run("coverage", "report", "--show-missing")
+    session.run("coverage", "report", "--show-missing", "--fail-under=100")
 
     session.run("coverage", "erase")