Undo removal of get_mac_context import

[jwiggins]

I removed this import in error as part of #558. It's needed by the Qt Quartz backend (enable.qt4.quartz).

@rahulporuri, @aaronayres35: This should be cherry-picked into the 5.0.0 branch.

[rahulporuri]

Changes LGTM but i'm not entirely sure why we can't just update the import to use kiva.quartz.mac_context in enable. I guess the import isnt just used in enable but in other places as well e.g. in user code?

Also, looking at enable.qt4.quartz, the import is from kiva.quartz import get_mac_context, ABCGI and im not entirely sure where ABCGI comes from?

[jwiggins]

ABCGI is a module in the kiva.quartz package, so that's how that import works.

I also briefly thought about changing the import in enable.qt4.quartz, but this fix restores behavior that might be depended on by external code, so I think it's best this way.

[rahulporuri]

ABCGI is a module in the kiva.quartz package, so that's how that import works.

Ahh. Makes sense.

... but this fix restores behavior that might be depended on by external code, so I think it's best this way.

Yeah. I agree.