add flake

Author: songgaoye

nix/testenv.nix

@@ -74,6 +74,22 @@ poetry2nix.mkPoetryEnv {
             sha256 = "sha256-UYm1LGEhwk/q4ogWarQbMlScfiNIZSc2VAuebn1OcuM=";
           };
         });
+
+        flake8 = super.execnet.overridePythonAttrs (old: {
+          src = fetchPypi {
+            pname = "flake8";
+            version = "7.1.1";
+            sha256 = "sha256-BJ0FhJHiKOA+Z7OQ8xG7+I/OLbqo+mc+euqHtxmLjTg=";
+          };
+        });
+
+        flake8_black = super.execnet.overridePythonAttrs (old: {
+          src = fetchPypi {
+            pname = "flake8_black";
+            version = "0.3.6";
+            sha256 = "sha256-UYm1LGEhwk/q4ogWarQbMlScfiNIZSc2VAuebn1Ocu2=";
+          };
+        });
       };
     in
     (lib.mapAttrs (