Add more contexts upon verifying APEX failure

I found this helpful while debugging.

Bug: N/A
Test: TH
Change-Id: Ia547dd83afbc4fffafebf2683c7136689abddb67
diff --git a/guest/microdroid_manager/src/main.rs b/guest/microdroid_manager/src/main.rs
index 8b676b8..d12bfd3 100644
--- a/guest/microdroid_manager/src/main.rs
+++ b/guest/microdroid_manager/src/main.rs
@@ -265,7 +265,7 @@
     // Verify the payload before using it.
     let extracted_data = verify_payload(metadata, saved_data.as_ref())
         .context("Payload verification failed")
-        .map_err(|e| MicrodroidError::PayloadVerificationFailed(e.to_string()))?;
+        .map_err(|e| MicrodroidError::PayloadVerificationFailed(format!("{:?}", e)))?;
 
     // In case identity is ignored (by debug policy), we should reuse existing payload data, even
     // when the payload is changed. This is to keep the derived secret same as before.
diff --git a/guest/microdroid_manager/src/payload.rs b/guest/microdroid_manager/src/payload.rs
index 98fe24b..8cb0f4e 100644
--- a/guest/microdroid_manager/src/payload.rs
+++ b/guest/microdroid_manager/src/payload.rs
@@ -16,7 +16,7 @@
 
 use crate::instance::ApexData;
 use crate::ioutil::wait_for_file;
-use anyhow::Result;
+use anyhow::{Context, Result};
 use log::{info, warn};
 use microdroid_metadata::{read_metadata, ApexPayload, Metadata};
 use std::time::Duration;
@@ -38,7 +38,8 @@
         .iter()
         .map(|apex| {
             let apex_path = format!("/dev/block/by-name/{}", apex.partition_name);
-            let extracted = apexutil::verify(&apex_path)?;
+            let extracted =
+                apexutil::verify(&apex_path).context(format!("Failed to parse {}", &apex_path))?;
             if let Some(manifest_name) = &extracted.name {
                 if &apex.name != manifest_name {
                     warn!("Apex named {} is named {} in its manifest", apex.name, manifest_name);