[proxmox_template] Fix error while uploading big ISO to Proxmox VE cluster (#6757)
* [proxmox_template] Fix error while uploading big ISO to Proxmox VE cluster
* Fix pep8 test
* Add changelog fragment
* Add notes about requests_toolbelt
* Check versions and file size
* Fix typo in notes
* Add unit test. Move try inside of each function.
* Fix sanity tests
* Add proxmoxer in requirements file
* Update integration tests
* Add proxmoxer into constraints.txt
* Address review comments
* Don't run tests on 2.6 python
* Disable Python 2.6 tests for other proxmox modules
(cherry picked from commit 2d6e369d81)
Co-authored-by: Sergei Antipov <greendayonfire@gmail.com>
