Adjust to the new sysconfig regime: use 'get_config_vars()' instead   of globals from sysconfig. Added 'prefix' and 'exec_prefix' to the list of variables that can be   expanded in installation directories (preserving the stupid old names   of 'sys_prefix' and 'sys_exec_prefix, though).
Adjust to the new sysconfig regime: use 'get_config_vars()' instead
  of globals from sysconfig.
Added 'prefix' and 'exec_prefix' to the list of variables that can be
  expanded in installation directories (preserving the stupid old names
  of 'sys_prefix' and 'sys_exec_prefix, though).

pypa/setuptools,pypa/setuptools,pypa/setuptools