feature: forbid import of testify packages as `_`

[dolmen]

import _ "github.com/stretchr/testify/assert"

Import of testify packages (assert, require, suite, mock, http) as _ is useless: those package don't do init magic.

They might have been imported like that in the past to workaround issues in dependency management tools (see the related case #37) but, now, in the Go modules era, this is obsolete.

Here are some cases in the wild:

• on GitHub: import _ "github.com/stretchr/testify/assert"
• on GitHub: _ "github.com/stretchr/testify/assert"
• on GitHub: _ "github.com/stretchr/testify/require"
• on GitHub: _ "github.com/stretchr/testify/suite"
• on GitHub: _ "github.com/stretchr/testify/mock"
• on GitHub: _ "github.com/stretchr/testify/http"

[hendrywiranto]

may I take this if this feature is desired?

[Antonboom]

@hendrywiranto, yes

it looks like enabled by default checkers.AdvancedChecker feel free to ask questions :)