Cannot install Beautiful Soup in Anaconda Python 3.6.4 Windows 10
One method that happened to work, and I am not sure how valid (safe) it is for other users:
I use Miniconda (smaller Anaconda packages) and installed bs4 through pip install bs4 instead of conda install bs4 (because it doesn't exist) in terminal whilst using my personal conda env to run a python program using BeautifulSoup. May save some trouble for others, but could be due to other settings on my device. 
I was using conda 4.8.3, Python 3.7.6, Windows 10 when this worked for me.
I install Beautiful Soup in Anaconda Python 3.6.4 Windows 10:

I downloaded and unpacked beautifulsoup4-4.6.3.tar.gz on my Desktop
I created an environment variable Pythonbasepath including the following directories:

C:\Users\Mika and Friends\Anaconda3
C:\Users\Mika and Friends\Anaconda3\Lib
C:\Users\Mika and Friends\Anaconda3\include
C:\Users\Mika and Friends\Anaconda3\DLLs
C:\Users\Mika and Friends\Anaconda3\Scripts
C:\Users\Mika and Friends\Anaconda3\Lib\site-packages

From the directory where I have extracted Beautiful Soup I try to run a command and I get an error: 


C:\Users\Mika and Friends\Desktop\bs4\bs4>python setup.py install
  'python' is not recognized as an internal or external command,
  operable program or batch file.

It seems something is wrong with the environment variable setup, but I cannot figure out what.