Convert to assert.NilError

Using:

  git grep -l '^\s\+assert\.Check(t, err)$' | \
    xargs sed -i -e 's/^\(\s\+assert\)\.Check(t, err)$/\1.NilError(t, err)/'

Signed-off-by: Daniel Nephin <dnephin@docker.com>

cmd/docker/docker_test.go

@@ -19,7 +19,7 @@ func TestClientDebugEnabled(t *testing.T) {
 	cmd.Flags().Set("debug", "true")
 
 	err := cmd.PersistentPreRunE(cmd, []string{})
-	assert.Check(t, err)
+	assert.NilError(t, err)
 	assert.Check(t, is.Equal("1", os.Getenv("DEBUG")))
 	assert.Check(t, is.Equal(logrus.DebugLevel, logrus.GetLevel()))
 }