Running yarn deploy gives TypeError: Cannot read property 'length' of undefined

[chrishobcroft]

I am trying to use the instructions here to deploy the protocol to the Ethereum Ephemery testnet.

Steps to reproduce:

1. clone the protocol repo with:

git clone https://github.com/livepeer/protocol.git

2. copy the .env.sample file to .env
3. add a private key, corresponding to an address with funds on Ephemery, to PRIVATE_KEY=
4. Add the following in hardhat.config.ts under networks:

        ethereumEphemeryDevnet: {
            url: `https://eth.ephemeral.zeus.fyi`,
            accounts: PRIVATE_KEY ? [`0x${PRIVATE_KEY}`] : undefined
        },

5. Set the defaultNetwork in hardhat.config.ts to ethereumEphemeryDevnet.
6. Run the following:

yarn
export LPT_DEPLOYMENT_EXPORT_PATH=~/Development/lpt_contracts.json
yarn deploy

7. See error:

Error: ERROR processing /home/ubuntu/protocol/deploy/deploy_contracts.ts:
TypeError: Cannot read property 'length' of undefined
    at getFrom (/home/ubuntu/protocol/node_modules/hardhat-deploy/src/helpers.ts:1642:14)
    at _deploy (/home/ubuntu/protocol/node_modules/hardhat-deploy/src/helpers.ts:537:9)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
    at async _deployOne (/home/ubuntu/protocol/node_modules/hardhat-deploy/src/helpers.ts:934:16)
    at DeploymentsManager.executeDeployScripts (/home/ubuntu/protocol/node_modules/hardhat-deploy/src/DeploymentsManager.ts:1232:19)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
error Command failed with exit code 1.