* added set_env_proxy function for setting proxy environment
Added set_env_proxy function, that set system http(s)_proxy
environment for fetching RPM if proxy settings set in yum.conf file
that fix Issue - #18979
* fix automatic field numbering specification
* changed if statement in setting http_proxy environment
* Change set_env_proxy function to function with decorator
That decorator set system proxy environment from yum.conf and revert
back to system configuration after fetching RPM
* Minor fix
- rename variable schem to scheme
- change 'in' to 'startswith'
* change decorator set_env_proxy to decorating through contextmanager
- added import contextmanager from contextlib
- set_env_proxy now decorating through contextmanager
- fix http/https setting environment principle