old_contents: import os
  from flask import Flask, abort
  
  app = Flask(__name__)
  
  @app.route('/')
  def hello():
          return 'python/flask'
  
  @app.route('/<env>')
  def get_enc(env):
          val = os.environ.get(env, None)
          if val:
                  return val
          else:
                  abort(404)
  
  
  
new_contents: import os
  from flask import Flask, abort
  
  app = Flask(__name__)
  
  @app.route('/')
  def hello():
          return 'python/flask'
  
  
  @app.route('/<env>')
  def get_enc(env):
          val = os.environ.get(env, None)
          if val:
                  return val
          else:
                  abort(404)
  
subject: correct flake8 issues