ValueError: Unable to expand environment variable in host setting

Environment information

• eth-brownie>=1.10.0,<2.0.0
• ganache-cli Version: 6.12.2
• solc Version: 0.6.6
• Python Version: 3.8.5
• OS: linux (ubuntu 20.04)

What was wrong?

Please include information like:

• what command you ran brownie run scripts/simple_collectible/deploy_simple.py --network rinkeby

• the code that caused the failure (see this link for help with formatting code)

• full output of the error you received

NftMixProject is the active project.
  File "brownie/_cli/__main__.py", line 64, in main
    importlib.import_module(f"brownie._cli.{cmd}").main()
  File "brownie/_cli/run.py", line 43, in main
    network.connect(CONFIG.argv["network"])
  File "brownie/network/main.py", line 40, in connect
    web3.connect(host, active.get("timeout", 30))
  File "brownie/network/web3.py", line 51, in connect
    uri = _expand_environment_vars(uri)
  File "brownie/network/web3.py", line 171, in _expand_environment_vars
    raise ValueError(f"Unable to expand environment variable in host setting: '{uri}'")
ValueError: Unable to expand environment variable in host setting: 'https://rinkeby.infura.io/v3/$WEB3_INFURA_PROJECT_ID'

How can it be fixed?

Fill this in if you know how the bug could be fixed.

[MelbyBaldove]

So I ran into this issue while I was doing test_lottery_unit.py of @PatrickAlphaC 's tutorial.

This might help you guys. Add this to the script

from dotenv import load_dotenv

load_dotenv()

[xAslan]

I also ran into this issue running brownie test -k test_get_entrance_fee --network rinkeby

solved by adding dotenv: .env to brownie-config.yaml