Vendor dependencies

Let's see how I like this workflow.

vendor/anyhow/tests/common/mod.rs

@@ -0,0 +1,14 @@
+use anyhow::{bail, Result};
+use std::io;
+
+pub fn bail_literal() -> Result<()> {
+    bail!("oh no!");
+}
+
+pub fn bail_fmt() -> Result<()> {
+    bail!("{} {}!", "oh", "no");
+}
+
+pub fn bail_error() -> Result<()> {
+    bail!(io::Error::new(io::ErrorKind::Other, "oh no!"));
+}