Older versions of virtualenv include their own "site" module that does not have the "getsitepackages" method. Add a check to verify its presence before calling it. Signed-off-by: Eric Callahan <arksine.code@gmail.com>
Use an enum to represent the sentinel rather than a singleton object. Signed-off-by: Eric Callahan <arksine.code@gmail.com>
Signed-off-by: Eric Callahan <arksine.code@gmail.com>
