Install pyqt via homebrew with `--with-python3` but still goes to Python 2 - python-3.x

Question

Here's my command and output (some command line arguments are left out). What is going wrong? Thank you.
$ brew reinstall pyqt --with-python3
==> Reinstalling pyqt --with-python3
==> Downloading http://downloads.sf.net/project/pyqt/PyQt4/PyQt-4.10.3/PyQt-mac-
Already downloaded: /Library/Caches/Homebrew/pyqt-4.10.3.tar.gz
==> Patching
patching file configure.py
==> python configure.py --confirm-license --bindir=/usr/local/Cellar/pyqt/4.10.3
==> python ./configure-ng.py --confirm-license --bindir=/usr/local/Cellar/pyqt/4
==> make
==> make install
==> Caveats
Set PYTHONPATH if you want Python to find your site-packages:
export PYTHONPATH=/usr/local/lib/python2.7/site-packages:$PYTHONPATH
==> Summary
🍺 /usr/local/Cellar/pyqt/4.10.3: 560 files, 18M, built in 6.6 minutes
UPDATE:
I think the formula of pyqt somehow hard-codes the python's version. For example it explicitly includes paths like python2.7/site-packages/. Here's part of the file:
def install
# On Mavericks we want to target libc++, this requires a non default qt makespec
if ENV.compiler == :clang and MacOS.version >= :mavericks
ENV.append "QMAKESPEC", "unsupported/macx-clang-libc++"
end
args = [ "--confirm-license",
"--bindir=#{bin}",
"--destdir=#{lib}/python2.7/site-packages",
"--sipdir=#{share}/sip" ]
# We need to run "configure.py" so that pyqtconfig.py is generated, which
# is needed by PyQWT (and many other PyQt interoperable implementations such
# as the ROS GUI libs). This file is currently needed for generating build
# files appropriate for the qmake spec that was used to build Qt. This method
# is deprecated and will be removed with SIP v5, so we do the actual compile
# using the newer configure-ng.py as recommended.
system "python", "configure.py", *args
(lib/'python2.7/site-packages').install 'pyqtconfig.py'
# On Mavericks we want to target libc++, this requires a non default qt makespec
if ENV.compiler == :clang and MacOS.version >= :mavericks
args << "--spec" << "unsupported/macx-clang-libc++"
end
system "python", "./configure-ng.py", *args
system "make"
system "make", "install"
end

Answer 1

You should check out this issue on Homebrew's git:
https://github.com/Homebrew/homebrew/issues/25735
We can no longer use the --with-python3 argument with pyside/pyqt/sip. Unfortunately, it seems like we can't use Homebrew for these modules in a while. They probably have to find another solution of handling the formulas for having Python 2.7 and Python3 installs first.
I scratched my head for days figuring this out. Ended up with installing PyQt from source.
Good luck.