From PEP 394
https://www.python.org/dev/peps/pep-0394/#for-python-script-publishers
In cases where the script is expected to be executed outside virtual environments,
developers will need to be aware of the following discrepancies across platforms and installation methods:
Older Linux distributions will provide a python command that refers to Python 2, and will likely not provide a python2 command.
Some newer Linux distributions will provide a python command that refers to Python 3.
Some Linux distributions will not provide a python command at all by default, but will provide a python3 command by default.
When potentially targeting these environments, developers may either use a Python package installation tool that rewrites shebang lines
for the installed environment, provide instructions on updating shebang lines interactively,
or else use more specific shebang lines that are tailored to the target environment.
On High Sierra and Mojave, virtualenv 16.x does not build when used with
system Python
Fall back to an older virtualenv version, which is known to work.
/usr/libexec/java_home is specific to macOS.
Language::Java::java_home_cmd is not implemented on Linux and raises
NotImplementedError.
Add private Language::Java::java_home_shell and use it instead of java_home_cmd.
Add public Language::Java::java_home for use by formulae.
Use 124 max line length everywhere. Also, reduce tap max line length to
189 as Homebrew/homebrew-core has that as a maximum now. In future
Homebrew/homebrew-core will also be reduced to 124 maximum line length.
Since ENV filtering became the default this has been chucking
erroneous warnings from both `brew doctor` and things like `brew install pygobject`
about needing to run:
```
echo 'import site; site.addsitedir("/usr/local/lib/python2.7/site-packages")' >> /Users/xyz/Library/Python/2.7/lib/python/site-packages/homebrew.pth
```
even though I had Homebrew's `python` installed.
