When you try to run the command pip install selenium through Jenkins, I stumbled upon the following problem:
Running setup.py install for selenium
... creating build/lib.linux-x86_64-2.7/selenium/webdriver/firefox/x86 copying py/selenium/webdriver/firefox/x86/x_ignore_nofocus.so -> build/lib.linux-x86_64-2.7/selenium/webdriver/firefox/x86 running install_lib creating /usr/local/lib/python2.7/dist-packages/selenium error: could not create '/usr/local/lib/python2.7/dist-packages/selenium': Permission denied
The problem was that I tried to install the module in the virtual environment being in a folder named "just for testing". To solve this problem, it is sufficient to rename the folder name so that it does not contain any spaces - "just_for_testing".