[PATCH] Capture stderr for 'git describe'

[Stephen Finucane]

On Thu, 2017-04-13 at 21:48 +0100, Stephen Finucane wrote:
> Capture the error messages thrown if git is not installed.
> 
> Signed-off-by: Stephen Finucane <stephen at that.guru>
> Fixes: 7b07b71e ("templates: Add Patchwork version")

Trivial fix. Applied.