pip-tools: pip-sync broken with pip 8.1.2

Should be fixed in pip-tools==1.7, which was released yesterday!

Hmm, yeah these changes affect pip-tools at the core. We need to carefully inspect how these data structures were refactored and how we need to follow those new patterns. For now, I’ll address this by issuing a warning that 8.1.2 is not supported in pip-tools 1.6.*, since I lack the time to properly fix this now.

I’ll change the codebase to match 8.1.2, but it won’t be a backward compatible fix, so I’ll roll a new minor release for it when it’s done.

This will be the situation:

• pip-tools < 1.7 will only support pip < 8.1.2
• pip-tools >= 1.7 will only support pip >= 8.1.2