Homebrew-core: Cannot link python3 in MacOS High Sierra

[Steffen911]

To help us debug your issue please explain:

• What you were trying to do (and why)
  I tried to install python3 on MacOS High Sierra. The only installed python version is the default 2.7 release. After successfully running brew install python3 I set it as the default python environment with brew link python3.

• What happened (include command output)
  This resulted in

Linking /usr/local/Cellar/python3/3.6.3... Error: Permission denied @ dir_s_mkdir - /usr/local/Frameworks

• What you expected to happen
  I expect it to set python3 as the standard python interpreter and use it, when I use $ python in the terminal

• Step-by-step reproduction instructions (by running brew install commands)

brew install python3
brew link python3

Using the --overwrite flag in brew link makes no difference.

Issue is the same as https://github.com/Homebrew/brew/issues/3308 (closed for formal errors)

[ilovezfs]

sudo mkdir -p /usr/local/Frameworks
sudo chown -R $(whoami) /usr/local/*
brew link python3

And the command is python3 not python.

[AndrewRayCode]

I'm having trouble understanding why this is closed. Homebrew is supposed to be able to install packages without needing root permissions, right? Why is the accepted solution to sudo make a directory? Doesn't this indicate a fundamental install bug with the package or Homebrew?

[ilovezfs]

@AndrewRayCode no. install makes the directory https://github.com/Homebrew/install/blob/master/install#L206

This is a product of old installs or OS upgrades.