SyntaxError: future feature annotations is not defined

[sergeygalkin]

Steps to reproduce

1. Build docker image
2. Try to start wally or python3 -m wally

root@wally:/# python3 -m wally test test configs-examples/ceph_raw.yaml
Traceback (most recent call last):
  File "/usr/lib/python3.6/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib/python3.6/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/opt/wally/wally/__main__.py", line 2, in <module>
    from .main import main
  File "/opt/wally/wally/main.py", line 23, in <module>
    from cephlib.texttable import Texttable
  File "/opt/cephlib/cephlib/__init__.py", line 1, in <module>
    from .raw_classes import (CephHealth, CephRole, OSDStatus, CephStatusCode, MonRole, CephRelease, OSDStoreType, PGState,
  File "/opt/cephlib/cephlib/raw_classes.py", line 1
    from __future__ import annotations
    ^
SyntaxError: future feature annotations is not defined
root@wally:/# wally 
Traceback (most recent call last):
  File "/usr/lib/python3.6/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib/python3.6/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/opt/wally/wally/__main__.py", line 2, in <module>
    from .main import main
  File "/opt/wally/wally/main.py", line 23, in <module>
    from cephlib.texttable import Texttable
  File "/opt/cephlib/cephlib/__init__.py", line 1, in <module>
    from .raw_classes import (CephHealth, CephRole, OSDStatus, CephStatusCode, MonRole, CephRelease, OSDStoreType, PGState,
  File "/opt/cephlib/cephlib/raw_classes.py", line 1
    from __future__ import annotations
    ^
SyntaxError: future feature annotations is not defined