Disabling http tests for guix

[Pjotr Prins]

On Friday, 6 January 2017 at 13:39:31 UTC, fredmanglis wrote:
> On Thursday, 5 January 2017 at 23:18:36 UTC, Joakim wrote:
>> Seem fairly small, but I could see why you wouldn't want to 
>> maintain them yourself.  If you're up for it, we could 
>> probably add a version flag to the test suite to disable these 
>> sections for packagers.

Similar to StdUnittest in 
https://github.com/dlang/phobos/pull/5927, I propose we
add version(StdNetworkunittest) and/or version(StdEnvUnittest) 
for those tests that require internet access or access to a 
directory outside the source tree (e.g. $TMPDIR) as these may not 
be available in containers and other restrictive build systems. 
Does that make sense?