Bitcoin Core requires python 3.5 at least. However, due to travis upsteam changes in the image, the installation of python3 no longer succeeds with brew. See e.g. https://travis-ci.org/bitcoin/bitcoin/jobs/631373413#L252
This should be fixed somehow.
Relevant copy of the log:
==> Upgrading python3
==> Downloading https://homebrew.bintray.com/bottles/python-3.7.6_1.mojave.bottl
==> Downloading from https://akamai.bintray.com/64/643d627c2b4fc03a3286c397d2992
######################################################################## 100.0%
==> Pouring python-3.7.6_1.mojave.bottle.tar.gz
Error: The `brew link` step did not complete successfully
The formula built, but is not symlinked into /usr/local
Could not symlink Frameworks/Python.framework/Headers
Target /usr/local/Frameworks/Python.framework/Headers
is a symlink belonging to python@2. You can unlink it:
brew unlink python@2
To force the link and overwrite all conflicting files:
brew link --overwrite python
To list all files that would be deleted:
brew link --overwrite --dry-run python
Possible conflicting files are:
/usr/local/Frameworks/Python.framework/Headers -> /usr/local/Cellar/python@2/2.7.17/Frameworks/Python.framework/Headers
/usr/local/Frameworks/Python.framework/Python -> /usr/local/Cellar/python@2/2.7.17/Frameworks/Python.framework/Python
/usr/local/Frameworks/Python.framework/Resources -> /usr/local/Cellar/python@2/2.7.17/Frameworks/Python.framework/Resources
/usr/local/Frameworks/Python.framework/Versions/Current -> /usr/local/Cellar/python@2/2.7.17/Frameworks/Python.framework/Versions/Current
==> /usr/local/Cellar/python/3.7.6_1/bin/python3 -s setup.py --no-user-cfg insta
==> /usr/local/Cellar/python/3.7.6_1/bin/python3 -s setup.py --no-user-cfg insta
==> /usr/local/Cellar/python/3.7.6_1/bin/python3 -s setup.py --no-user-cfg insta
==> Caveats
Python has been installed as
/usr/local/bin/python3
Unversioned symlinks `python`, `python-config`, `pip` etc. pointing to
`python3`, `python3-config`, `pip3` etc., respectively, have been installed into
/usr/local/opt/python/libexec/bin
If you need Homebrew's Python 2.7 run
brew install python@2
You can install Python packages with
pip3 install <package>
They will install into the site-package directory
/usr/local/lib/python3.7/site-packages
See: https://docs.brew.sh/Homebrew-and-Python
==> Summary
🍺 /usr/local/Cellar/python/3.7.6_1: 3,977 files, 60.8MB
Removing: /usr/local/Cellar/python/3.7.5... (4,049 files, 61.9MB)
Removing: /Users/travis/Library/Caches/Homebrew/python--3.7.5.mojave.bottle.tar.gz... (14.8MB)
