requirements: Update flake8-future-import to 0.4.0

- Add two older future imports
- Issue an error when a future import does not exist
- Define which is the oldest Python version to be supported so that
  already mandatory features can be ignored and not yet supported
  features default to forbidden (ignoring the lower error code).
- Use return code of 1 if errors occurred

.flake8

@@ -30,7 +30,7 @@ exclude = .venv,.hypothesis,.git,__pycache__,resources.py
 # D211: No blank lines allowed before class docstring
 #       (PEP257 got changed, but let's stick to the old standard)
 # D402: First line should not be function's signature (false-positives)
-# FI10 - FI15: __future__ import missing
+# FI10 - FI17: __future__ import missing
 # H101: Use TODO(NAME)
 # H201: bare except
 # H238: Use new-stule classes
@@ -43,7 +43,7 @@ ignore =
     L101,L102,L103,L201,L202,L203,L204,L207,L302,
     P101,P102,P103,
     D102,D103,D104,D105,D209,D211,D402,
-    FI10,FI11,FI12,FI13,FI14,FI15,
+    FI10,FI11,FI12,FI13,FI14,FI15,FI16,FI17,
     H101,H201,H238,H301,H306
 max-complexity = 12
 putty-auto-ignore = True

misc/requirements/requirements-flake8.txt

@@ -4,7 +4,7 @@ flake8-copyright==0.1
 flake8-debugger==1.4.0
 flake8-deprecated==1.0
 flake8-docstrings==0.2.6
-flake8-future-import==0.3.2
+flake8-future-import==0.4.0
 flake8-mock==0.2
 flake8-pep3101==0.3
 flake8-putty==0.3.2