error: Print errors using Display impl

I have been running into Debug-printed error messages too often and
needing to look up in the source code each level of nested errors to
find out from the comment on the error variant what the short name of
the variant means in human terms. Worse, many errors (like the one shown
below) already had error strings written but were being printed from the
calling code in the less helpful Debug representation anyway.

Before:
    [ERROR:src/main.rs:705] The architecture failed to build the vm: NoVarEmpty

After:
    [ERROR:src/main.rs:705] The architecture failed to build the vm: /var/empty doesn't exist, can't jail devices.

TEST=cargo check --all-features
TEST=FEATURES=test emerge-amd64-generic crosvm

Change-Id: I77122c7d6861b2d610de2fff718896918ab21e10
Reviewed-on: https://chromium-review.googlesource.com/1469225
Commit-Ready: David Tolnay <dtolnay@chromium.org>
Tested-by: David Tolnay <dtolnay@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/tests/plugins.rs b/tests/plugins.rs
index 6176a32..e95cc07 100644
--- a/tests/plugins.rs
+++ b/tests/plugins.rs
@@ -24,7 +24,7 @@ struct RemovePath(PathBuf);
 impl Drop for RemovePath {
     fn drop(&mut self) {
         if let Err(e) = remove_file(&self.0) {
-            eprintln!("failed to remove path: {:?}", e);
+            eprintln!("failed to remove path: {}", e);
         }
     }
 }