Describes the cause and action for error messages.
Error Message(English)：
installed but not found
Module Successfully Installed, but Not Found in IPython - Stack ...
https://stackoverflow.com/questions/26599443/module-successfully-installed-but-not-found-in-ipython
Matplotlib installed but not found mac python 2.7
https://stackoverflow.com/questions/46066480/matplotlib-installed-but-not-found-mac-python-2-7
IPython command not found Terminal OSX. Pip installed
https://stackoverflow.com/questions/16745923/ipython-command-not-found-terminal-osx-pip-installed
iPython installed but not found
https://stackoverflow.com/questions/34441943/ipython-installed-but-not-found
Scikit-learn installed but not found,
https://stackoverflow.com/questions/29391630/scikit-learn-installed-but-not-found
IPython command not found Terminal OSX. Pip installed - Stack ...
https://stackoverflow.com/questions/16745923/ipython-command-not-found-terminal-osx-pip-installed/22・・・
debian - How to find my pip? - Unix & Linux Stack Exchange
https://unix.stackexchange.com/questions/287154/how-to-find-my-pip
Make Command Not Found - Ask Ubuntu
https://askubuntu.com/questions/192645/make-command-not-found
Gentoo Forums :: View topic - [SOLVED] gexiv2 installed but not ...
https://forums.gentoo.org/viewtopic-p-8004224.html?sid=78c9550dad12e80757e505fe50bed583