No prompt in pyvenv.cfg makes venv incorrectly empty

[matthubb]

The new ini check will incorrectly blank out env if there is no prompt value in the ini file.

powerline-go/segment-virtualenv.go

Line 19 in fe0a2a4

env = cfg.Section("").Key("prompt").String()

I'm not that familiar with golang, perhaps assigning the output of the ini lookup to a temporary value and checking it's not empty before overwriting env would suitably resolve this issue?

new_env = cfg.Section("").Key("prompt").String()
if new_env != "" {
        env = new_env
}

[elebertus]

#387 - this change resolved the issue for me. Waiting for review.