Unwrap in I2C transaction

Let's say I have an I2C transaction like this one below. Clearly, any of the operations can fail and in this case error should be returned (At least I2c interface allows this). To simulate such failed operation, I was expecting with_error approach to work (Line 3).

let mut i2c = Mock::new(&[
    I2cTransaction::transaction_start(0x76),
    I2cTransaction::write(0x76, vec![0x88]), // .with_error(I2cErrorKind::Other),
    I2cTransaction::read(0x76, vec![0xCC, 0x6D, 0x1B, 0x68, 0x32, 0x00]),
    I2cTransaction::write(0x76, vec![0xA1]),
    I2cTransaction::read(0x76, vec![0x4B]),
    I2cTransaction::write(0x76, vec![0xE1]),
    I2cTransaction::read(0x76, vec![0x70, 0x01, 0x00, 0x13, 0x21, 0x03, 0x1E]),
    I2cTransaction::write(0x76, vec![0xFA]),
    I2cTransaction::read(0x76, vec![0x7E, 0x9B, 0x00, 0x5D, 0xC2])
        .with_error(I2cErrorKind::Other),
    I2cTransaction::transaction_end(0x76),
])

But it does not and causes panic instead. This panic originates from unwrap on the following line:
https://github.com/dbrgn/embedded-hal-mock/blob/e11348e9d34ef5809eb3b13979bab0efd7d92a44/src/eh1/i2c.rs#L273
For me it seems ? would be more appropriate.

Start at src/eh1/i2c.rs line 273, where the issue reports that an I2C operation error is unwrapped, and inspect the surrounding transaction error handling. Check the existing I2C mock tests and add coverage for the with_error case; done means the configured error is returned instead of causing a panic.