Improved user-facing messages

tests/pending_manager_test.py

Index: tests/pending_manager_test.py
diff --git a/tests/pending_manager_test.py b/tests/pending_manager_test.py
index efef86f109eee3ce27deaafa82782c19fbd198f0..96b87efad0445c07a158f0faa9553b060a6bc149 100755
--- a/tests/pending_manager_test.py
+++ b/tests/pending_manager_test.py
@@ -165,19 +165,22 @@ class TestPendingManager(mocks.TestCase):
 
   def testNoVerification(self):
     try:
-      # Need at least one verification.
       self._get_pc([], [])
-      self.fail()
-    except AssertionError:
+    except ValueError:

[ghost stip (do not use), 2014/01/02 20:56:33]

I'm not sure I understand what's going on here. Can you walk me through it?

[pgervais, 2014/01/02 22:16:48]

_get_pc instantiate a PendingManager using no verifiers (thus the empty list.)
This must trigger an exception. I did two things:
- move the code that displays an error message in a "else" section, because
every exception that self.fail raises have no reason to be excepted.
- replaced in PendingManager an invocation of assert by a proper test and a
raise ValueError, because it's more appropriate than assert.

Changing the exception raised has possibly some consequence on existing code,
but since catching AssertionError is hardly done, that shouldn't be a problem.

       pass
+    else:
+      self.fail(msg="A PendingManager must require at least one verifier.")
+
     try:
       # Cannot have the same verifier two times.
       self._get_pc(
           [fake.FakeVerifier(base.SUCCEEDED)],
           [fake.FakeVerifier(base.SUCCEEDED)])
-      self.fail()
     except AssertionError:
       pass
+    else:
+      self.fail(msg="A PendingManager should not accept the same verifier"
+                "two times.")
 
   def _check_1(self, pc, result):
     issue = 31337