FEAT: Add flake8 (#267)

* init flake8

* exclude nostr client, and add ds_store to gitignore

* fix flake8 F811 issue, redefinition of unused variables

* add flake8 to workflow

* F401 unused imports

* F541 f-string is missing placeholders

* E501 line too long > 150 characters

* E722 no bare except

* E402 module level import not at top of file

* F405 no star imports

* E712 comparison to False should be 'if cond is False:'

* F841 local variable is assigned to but never used

* E266 too many leading '#' for block comment

* E265, E261

* E713 test for membership should be 'not in'

* E711, E741

E741 ambiguous variable name 'l'
E711 comparison to None should be 'if cond is None:'

* flake config

* isort

* refactor makefile flake8 usage

* reflaking the rebase

* black

* fix tests?

* black

* fix line lenght it test_cli

* sort out makefile

* fix strings

* reintroduce black-check

* reflake and mypy

* isort

* Update cashu/wallet/wallet.py

Co-authored-by: Angus Pearson <angus@toaster.cc>

* Update cashu/mint/ledger.py

Co-authored-by: Angus Pearson <angus@toaster.cc>

---------

Co-authored-by: Angus Pearson <angus@toaster.cc>

tests/test_mint.py

@@ -5,13 +5,10 @@ import pytest
 from cashu.core.base import BlindedMessage, Proof
 from cashu.core.crypto.b_dhke import step1_alice
 from cashu.core.helpers import calculate_number_of_blank_outputs
-from cashu.core.migrations import migrate_databases
-
-SERVER_ENDPOINT = "http://localhost:3338"
-
 from cashu.core.settings import settings
 from cashu.mint.ledger import Ledger
-from tests.conftest import ledger
+
+SERVER_ENDPOINT = "http://localhost:3338"
 
 
 async def assert_err(f, msg):