I am really not certain what generates the problem in your case, but the code below runs for me without any issues (OSX, the same version of conda as yours).
Creation of the environment:
conda create -n test_env python=3.6.3 anaconda
-n test_env sets the name of the environment to test_env
python=3.6.3 anaconda says that you want to use in this environment python in version 3.6.3 and package anaconda. You can place there all the items you need, separated with spaces, e.g. SQLite matplotlib requests, and define their versions the same way as for python.
conda activate test_env
Getting rid of it
conda remove -n test_env --all
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