Add flake8 config

.flake8

@@ -1,4 +1,4 @@
-# use .flake8 until we can move this config to pyproject.toml
+# use .flake8 until we can move this config to pyproject.toml (not possible yet (27/02/2024) according to issue below)
 # https://github.com/PyCQA/flake8/issues/234
 
 [flake8]
@@ -37,9 +37,6 @@ extend-ignore =
     # W503 line break before binary operator
     W503,
 
-    # C901 too complex function (ignore temporarily)
-    C901,
-
 # set max-line-length to be black compatible, as suggested in the black docs
 # https://github.com/psf/black/blob/d038a24ca200da9dacc1dcb05090c9e5b45b7869/docs/the_black_code_style/current_style.md#line-length
 max-line-length = 88
@@ -55,3 +52,5 @@ show-source = True
 
 # count errors and warnings
 statistics = True
+exclude = 
+    .venv