python3 -m venv vevn
source venv/bin/active
pip install pip --upgrade
# директория для скачивания пакетов
mkdir pkg
cd pkg
# отдельно скачиваю последнею версию pip
pip download pip
# скачиваю необходимые пакеты с зависимостями
pip download -r ../requirements.txt

python3 -m venv vevn
source venv/bin/active
# устанавливаю ранее скаченный pip (версия может быть другая)
pip install pkg/pip-20.1-py2.py3-none-any.whl
# установка пакетов из списка requirements.txt, пакеты должны лежать в pkg (директория)
pip install --no-index --find-links pkg -r requirements.txt

# вывод консоли у меня
pip install --no-index --find-links pkg -r requirements.txt 
Looking in links: pkg
Processing ./pkg/Flask-1.1.2-py2.py3-none-any.whl
Processing ./pkg/Flask_WTF-0.14.3-py2.py3-none-any.whl
Processing ./pkg/et_xmlfile-1.0.1.tar.gz
Processing ./pkg/openpyxl-3.0.3.tar.gz
Processing ./pkg/jdcal-1.4.1-py2.py3-none-any.whl
Processing ./pkg/pylint-2.5.2-py3-none-any.whl
Processing ./pkg/itsdangerous-1.1.0-py2.py3-none-any.whl
Processing ./pkg/Jinja2-2.11.2-py2.py3-none-any.whl
Processing ./pkg/Werkzeug-1.0.1-py2.py3-none-any.whl
Processing ./pkg/click-7.1.2-py2.py3-none-any.whl
Processing ./pkg/WTForms-2.3.1-py2.py3-none-any.whl
Processing ./pkg/mccabe-0.6.1-py2.py3-none-any.whl
Processing ./pkg/isort-4.3.21-py2.py3-none-any.whl
Processing ./pkg/toml-0.10.1-py2.py3-none-any.whl
Processing ./pkg/astroid-2.4.1-py3-none-any.whl
Processing ./pkg/MarkupSafe-1.1.1-cp37-cp37m-manylinux1_x86_64.whl
Processing ./pkg/typed_ast-1.4.1-cp37-cp37m-manylinux1_x86_64.whl
Processing ./pkg/wrapt-1.12.1.tar.gz
Processing ./pkg/lazy_object_proxy-1.4.3-cp37-cp37m-manylinux1_x86_64.whl
Processing ./pkg/six-1.14.0-py2.py3-none-any.whl
Could not build wheels for et-xmlfile, since package 'wheel' is not installed.
Could not build wheels for openpyxl, since package 'wheel' is not installed.
Could not build wheels for wrapt, since package 'wheel' is not installed.
Installing collected packages: itsdangerous, MarkupSafe, Jinja2, Werkzeug, click, Flask, WTForms, Flask-WTF, et-xmlfile, jdcal, openpyxl, mccabe, isort, toml, typed-ast, wrapt, lazy-object-proxy, six, astroid, pylint
    Running setup.py install for et-xmlfile ... done
    Running setup.py install for openpyxl ... done
    Running setup.py install for wrapt ... done
Successfully installed Flask-1.1.2 Flask-WTF-0.14.3 Jinja2-2.11.2 MarkupSafe-1.1.1 WTForms-2.3.1 Werkzeug-1.0.1 astroid-2.4.1 click-7.1.2 et-xmlfile-1.0.1 isort-4.3.21 itsdangerous-1.1.0 jdcal-1.4.1 lazy-object-proxy-1.4.3 mccabe-0.6.1 openpyxl-3.0.3 pylint-2.5.2 six-1.14.0 toml-0.10.1 typed-ast-1.4.1 wrapt-1.12.1

Flask==1.1.2
Flask-WTF==0.14.3
et-xmlfile==1.0.1
openpyxl==3.0.3
jdcal==1.4.1
pylint==2.5.2

# установка одного пакета из архива
pip install ./pkg-name.tar.gz