csvkit: csvsql: Lots of error messages when using Homebrew Python 2.7 on macOS

I have encountered a lot of error messages when using csvsql. However, csvsql is fully functional. This can be reproduced by simply calling csvsql without parameters. I installed csvkit by pip from Homebrew Python 2.7

My system configuration is as follows from brew config:

HOMEBREW_VERSION: 1.1.9
ORIGIN: https://github.com/Homebrew/brew.git
HEAD: 664d0c67d5947605c914c4c56ebcfaa80cb6eca0
Last commit: 2 days ago
Core tap ORIGIN: https://github.com/Homebrew/homebrew-core
Core tap HEAD: 662c74e3f73c00fb55878d0c93c319cdefeb0983
Core tap last commit: 3 hours ago
HOMEBREW_PREFIX: /usr/local
HOMEBREW_REPOSITORY: /usr/local/Homebrew
HOMEBREW_CELLAR: /usr/local/Cellar
HOMEBREW_BOTTLE_DOMAIN: https://homebrew.bintray.com
CPU: octa-core 64-bit haswell
Homebrew Ruby: 2.0.0-p648
Clang: 8.0 build 800
Git: 2.11.0 => /usr/local/bin/git
Perl: /usr/local/bin/perl => /usr/local/Cellar/perl/5.24.0_1/bin/perl
Python: /usr/local/bin/python => /usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/bin/python2.7
Ruby: /usr/local/bin/ruby => /usr/local/Cellar/ruby/2.4.0/bin/ruby
Java: 1.8.0_20
macOS: 10.12.3-x86_64
Xcode: 8.2.1
CLT: 8.2.0.0.1.1480973914
X11: 2.7.11 => /opt/X11

The error messages are (repeated many times):

/usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pkgutil.py:186: ImportWarning: Not importing directory '/usr/local/lib/python2.7/site-packages/google': missing __init__.py
/usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pkgutil.py:186: ImportWarning: Not importing directory '/usr/local/lib/python2.7/site-packages/mpl_toolkits': missing __init__.py
/usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pkgutil.py:186: ImportWarning: Not importing directory '/usr/local/lib/python2.7/site-packages/logilab': missing __init__.py