Instead of printing an io::Error::display, print the the path that failed

[czipperz]

If you make a project and add the following to the Cargo.toml:

[workspace]
members = [""]

[dependencies]
x = { path = "x" }

You get the error message:

$ RUST_BACKTRACE=1 cargo test -q

Caused by:
  No such file or directory (os error 2)

[czipperz]

So it turns out passing -q removes the path from the error message (which I was doing above):

error: failed to read `/home/czipperz/test4/x/Cargo.toml`

Caused by:
  No such file or directory (os error 2)

In any case it's different than the normal message (no workspace):

error: failed to load source for a dependency on `x`

Caused by:
  Unable to update /home/czipperz/test4/x

Caused by:
  failed to read `/home/czipperz/test4/x/Cargo.toml`

Caused by:
  No such file or directory (os error 2)