const module not exposed

[valentingregoire]

Description of the problem, including code/CLI snippet

The const module is not exported, therefore, one cannot access any const properly.

Expected Behavior

One can simply access the consts

Actual Behavior

Right now, it is possible to access the consts with gitlab.const.XYZ, but this is not the most ideal situation I believe.

Specifications

• python-gitlab version: 4.4.0
• API version you are using (v3/v4): v4
• Gitlab server version (or gitlab.com): most recent

[nejch]

As discussed in #2820 we'll keep this as is - it's expected that the constants aren't exposed at the root package level.