Standard error is printed twice for some failing commands

[alexcrichton]

🐛 Bug description

I was testing something out today and ran:

$ git clone https://github.com/rustwasm/wasm-pack-template
$ cd wasm-pack-template
$ wasm-pack build

  [1/9] Checking `rustc` version...
  [2/9] Checking crate configuration...
  [3/9] Adding WASM target...
  info: component 'rust-std' for target 'wasm32-unknown-unknown' is up to date
  [4/9] Compiling to WASM...
  error: failed to parse manifest at `/home/alex/code/wasm-pack-template/Cargo.toml`

  Caused by:
|   Invalid character `{` in package name: `{{project-name}}`
Compiling your crate to WebAssembly
Caused by: Process exited with exit code: 101: `cargo build` did not exit successfully.

stdout:

stderr:

error: failed to parse manifest at `/home/alex/code/wasm-pack-template/Cargo.toml`

Caused by:
  Invalid character `{` in package name: `{{project-name}}`