Pip upgrade command update for django installation tutorial

[nikhiljohn10]

pip command update

• [x] Updated pip upgrade command
• [x] Added note on pip upgrade option

Ref: https://github.com/DjangoGirls/tutorial/pull/1683#issuecomment-727185235 by @das-g

[das-g]

As I've written in https://github.com/DjangoGirls/tutorial/pull/1683#issuecomment-727189372, I don't think python -m pip ... vs. just pip ... was a Windows specific issue. If possible, I'd prefer to keep the instructions for different operating systems the same. So I think we should:

• test whether the command works fine without python -m on Windows, MacOS and Linux
• depending on the result, either keep python -m in the common instruction for all three, or remove it from that common instruction

[nikhiljohn10]

As far as I know, I use Linux at home and Mac at the office and both work well with pip install -U pip. I really do not like programming on a windows pc unless it's just HTML and CSS. So I have to test it. I'll let you know the result.

[nikhiljohn10]

(myvenv) C:\Users\me\Desktop\mysite>pip -V
pip 20.2.3 from c:\users\me\desktop\mysite\myvenv\lib\site-packages\pip (python 3.9)

(myvenv) C:\Users\me\Desktop\mysite>python -m pip -V
pip 20.2.3 from C:\Users\me\Desktop\mysite\myvenv\lib\site-packages\pip (python 3.9)

(myvenv) C:\Users\me\Desktop\mysite>pip install -U pip
Collecting pip
  Using cached pip-20.2.4-py2.py3-none-any.whl (1.5 MB)
Installing collected packages: pip
  Attempting uninstall: pip
    Found existing installation: pip 20.2.3
    Uninstalling pip-20.2.3:
      Successfully uninstalled pip-20.2.3
ERROR: Could not install packages due to an EnvironmentError: [WinError 5] Access is denied: 'C:\\Users\\me\\AppData\\Local\\Temp\\pip-uninstall-o1mvxqmn\\pip.exe'
Consider using the `--user` option or check the permissions.

(myvenv) C:\Users\me\Desktop\mysite>pip install --user -U pip
ERROR: Can not perform a '--user' install. User site-packages are not visible in this virtualenv.

(myvenv) C:\Users\me\Desktop\mysite>python -m pip install -U pip
Collecting pip
  Using cached pip-20.2.4-py2.py3-none-any.whl (1.5 MB)
Installing collected packages: pip
  Attempting uninstall: pip
    Found existing installation: pip 20.2.3
    Uninstalling pip-20.2.3:
      Successfully uninstalled pip-20.2.3
Successfully installed pip-20.2.4

@das-g The above result I got from testing Python and Pip concludes that the problem still exists in Windows OS. Thus the proposed changes in this PR are necessary for Windows users.

[das-g]

Researching why that might be, I've now read Why you should use python -m pip.

It explains why pip install -U pip doesn't work on Windows (not even with the virtual environment activated, even though the pip from the virtual environment is being used) and, as the title says, why one should use python -m pip instead of just pip even when not on Windows and even when working with virtual environments. TL;DR:

• finer control over Python version used to call pip (and by extension, for which Python pip will install the packages)
• consistency between different operating systems
• consistency between with vs. without virtual environments
• show and teach best practices

Therefore: Sorry for the back and forth, but I now think we should stick to the python -m pip way to call pip for all operating systems.