flake8: silence all warnings/errors

these need to be fixed in separate commits/PRs, always keeping the
tests working (not failing).

setup.cfg

@@ -12,5 +12,20 @@ pep8ignore =
  docs/source/conf.py ALL  # sphinx stuff, automatically generated, don't check this
 
 [flake8]
-ignore = E124,E125,F403
+ignore =
+    E121,  # continuation line under-indented for hanging indent
+    E122,  # continuation line missing indentation or outdented
+    E124,  # closing bracket does not match visual indentation
+    E226,  # missing whitespace around arithmetic operator
+    E265,  # block comment should start with '# '
+    E302,  # expected 2 blank lines, found 1
+    E303,  # too many blank lines (N)
+    E305,  # expected 2 blank lines after class or function definition, found 1
+    E402,  # module level import not at top of file
+    E731,  # do not assign a lambda expression, use a def
+    F401,  # 'X' imported but unused
+    F403,  # 'from x import *' used; unable to detect undefined names
+    F405,  # 'X' may be undefined, or defined from star imports
+    F821,  # undefined name 'X'
+    F841,  # local variable 'X' is assigned to but never used
 max-line-length = 120