input: Write a python function to make a GET request to a specified URL and return the content if successful or an error message otherwise.
  assert get_url_content('https://example.com/test') == 'expected content'
  assert get_url_content('https://example.com/invalid') == 'Request failed with status code: 404'
  assert get_url_content('https://example.com/redirect') == 'Request failed with status code: 301'
output: import requests
  
  def get_url_content(url):
      try:
          response = requests.get(url)
          if response.status_code == 200:
              return response.text
          else:
              return f'Request failed with status code: {response.status_code}'
      except requests.RequestException as e:
          return f'Request failed with error: {str(e)}'