Unable to install boto3

Don't use sudo in a virtual environment because it ignores the environment's variables and therefore sudo pip refers to your global pip installation.

So with your environment activated, rerun pip install boto3 but without sudo.

try this way:

python -m pip install --user boto3

There is another possible scenario that might get some people as well (if you have python and python3 on your system):

pip3 install boto3

Note the use of pip3 indicates the use of Python 3's pip installation vs just pip which indicates the use of Python 2's.