Auth fail on sbt new

## Steps

Set up a template project on a private Gitlab instance using the following `build.properties`:

```
sbt.version=1.6.2
giter8.version=0.14.0
```

then run

```
sbt new git@gitlab.com:company/private/template-project.g8.git
```

## Problem

I'm getting the following error

```
git@gitlab.com:company/private/template-project.g8.git: Auth fail
```

However, if I install g8 using Coursier, it just works:

```scala
g8 git@gitlab.com:company/private/template-project.g8.git
```

Cloning the repo works just fine, too
```
git clone git@gitlab.com:company/private/template-project.g8.git
```

## Expectation

The `sbt new` command creates the project without errors.

## Notes

For what it's worth, the above versions in `build.properties` match my local versions for both sbt (installed via Homebrew) and giter8 (installed via Coursier as a workaround for `sbt new`). The problem should have been solved in https://github.com/foundweekends/giter8/pull/583, but I'm using the latest sbt/g8 versions and still getting the `Auth fail` error.