PERMISSION DENIDED ERRNO 13

[snippsat]

Should not need to use sudo as virtual environment should be user based.

I am trying to install flake8 on virtualenv

How are you creating the virtual environment,is calculator your environment folder do you see see (calculator)?
Now also virtual environment is build into python trough venv.
Example:

tom@tom:~$ python -m venv my_env
tom@tom:~$ cd my_env
tom@tom:~/my_env$ source bin/activate

# Active see (my_env)
(my_env) tom@tom:~/my_env$ pip install flake8
Collecting flake8  
Installing collected packages: pyflakes, mccabe, pycodestyle, flake8
Successfully installed flake8-3.6.0 mccabe-0.6.1 pycodestyle-2.4.0 pyflakes-2.0.0

(my_env) tom@tom:~/my_env$ python 
Python 3.7.2 (default, Jan 16 2019, 23:14:35) 
[GCC 7.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import flake8
>>> flake8.__version__
'3.6.0'
>>> exit()