Tests that fail with 1 error report "True" instead of "1" for the number of errors

[drewbanin]

Issue

Issue description

Tests that fail with 1 error report "True" instead of "1" for the number of errors. This happens, I think, because we fetch an Agate dataframe, which assumes that the number of failures is a boolean instead of an integer.

Results

Expected: [FAIL 1]
Received: [Fail True]

System information

= 0.11.1

The python version you're using (probably the output of python --version)
3.7

Steps to reproduce

-- models/test_model.sql

select null as id

# schema.yml

version: 2

models:
  - name: test_model:
  - columns:
    name: id
    tests:
      - not_null