python could not find a version that satisfies the requirement code example

Example 1: linux Could not find a version that satisfies the requirement

#instead of requirements.txt use
python3 -m pip install <pkg>
# Some packages just want your personal attention...

Example 2: pip error could not find a version that satisfies the requirement

$ curl https://pypi.org

The requestors Network has been blacklisted due to excessive request volume. 
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