Tighten up psf/black and flake8 (#2024)

* Tighten up psf/black and flake8

* Fix some tests

* Fix some E741

* Fix some E741

* updating DIRECTORY.md

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

project_euler/problem_08/sol1.py

@@ -53,7 +53,7 @@ N = """73167176531330624919225119674426574742355349194934\
 def solution(n):
     """Find the thirteen adjacent digits in the 1000-digit number n that have
     the greatest product and returns it.
- 
+
     >>> solution(N)
     23514624000
     """

project_euler/problem_08/sol2.py

@@ -56,7 +56,7 @@ N = (
 def solution(n):
     """Find the thirteen adjacent digits in the 1000-digit number n that have
     the greatest product and returns it.
- 
+
     >>> solution(N)
     23514624000
     """

project_euler/problem_08/sol3.py

@@ -60,7 +60,7 @@ def streval(s: str) -> int:
 def solution(n: str) -> int:
     """Find the thirteen adjacent digits in the 1000-digit number n that have
     the greatest product and returns it.
- 
+
     >>> solution(N)
     23514624000
     """