diff --git a/rust/Cargo.lock b/rust/Cargo.lock
--- a/rust/Cargo.lock
+++ b/rust/Cargo.lock
@@ -286,9 +286,9 @@
 
 [[package]]
 name = "format-bytes"
-version = "0.2.1"
+version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8030ff4b04f0ca1c612d6fe49f2fc18caf56fb01497cb370b41cfd36d89b3b06"
+checksum = "1c4e89040c7fd7b4e6ba2820ac705a45def8a0c098ec78d170ae88f1ef1d5762"
 dependencies = [
  "format-bytes-macros",
  "proc-macro-hack",
diff --git a/rust/hg-core/Cargo.toml b/rust/hg-core/Cargo.toml
--- a/rust/hg-core/Cargo.toml
+++ b/rust/hg-core/Cargo.toml
@@ -28,7 +28,7 @@
 memmap = "0.7.0"
 zstd = "0.5.3"
 rust-crypto = "0.2.36"
-format-bytes = "0.2.0"
+format-bytes = "0.2.2"
 
 # We don't use the `miniz-oxide` backend to not change rhg benchmarks and until
 # we have a clearer view of which backend is the fastest.
diff --git a/rust/hg-core/src/config/layer.rs b/rust/hg-core/src/config/layer.rs
--- a/rust/hg-core/src/config/layer.rs
+++ b/rust/hg-core/src/config/layer.rs
@@ -7,7 +7,7 @@
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 
-use crate::errors::{HgError, IoResultExt};
+use crate::errors::HgError;
 use crate::utils::files::{get_bytes_from_path, get_path_from_bytes};
 use format_bytes::{format_bytes, write_bytes, DisplayBytes};
 use lazy_static::lazy_static;
@@ -74,7 +74,7 @@
                 layer.add(section, item, value, None);
             } else {
                 Err(HgError::abort(format!(
-                    "malformed --config option: '{}' \
+                    "abort: malformed --config option: '{}' \
                     (use --config section.name=value)",
                     String::from_utf8_lossy(arg),
                 )))?
@@ -147,6 +147,7 @@
         let mut section = b"".to_vec();
 
         while let Some((index, bytes)) = lines_iter.next() {
+            let line = Some(index + 1);
             if let Some(m) = INCLUDE_RE.captures(&bytes) {
                 let filename_bytes = &m[1];
                 // `Path::parent` only fails for the root directory,
@@ -158,8 +159,17 @@
                 // `Path::join` with an absolute argument correctly ignores the
                 // base path
                 let filename = dir.join(&get_path_from_bytes(&filename_bytes));
-                let data =
-                    std::fs::read(&filename).when_reading_file(&filename)?;
+                let data = std::fs::read(&filename).map_err(|io_error| {
+                    ConfigParseError {
+                        origin: ConfigOrigin::File(src.to_owned()),
+                        line,
+                        message: format_bytes!(
+                            b"cannot include {} ({})",
+                            filename_bytes,
+                            format_bytes::Utf8(io_error)
+                        ),
+                    }
+                })?;
                 layers.push(current_layer);
                 layers.extend(Self::parse(&filename, &data)?);
                 current_layer = Self::new(ConfigOrigin::File(src.to_owned()));
@@ -184,12 +194,7 @@
                     };
                     lines_iter.next();
                 }
-                current_layer.add(
-                    section.clone(),
-                    item,
-                    value,
-                    Some(index + 1),
-                );
+                current_layer.add(section.clone(), item, value, line);
             } else if let Some(m) = UNSET_RE.captures(&bytes) {
                 if let Some(map) = current_layer.sections.get_mut(&section) {
                     map.remove(&m[1]);
@@ -202,7 +207,7 @@
                 };
                 return Err(ConfigParseError {
                     origin: ConfigOrigin::File(src.to_owned()),
-                    line: Some(index + 1),
+                    line,
                     message,
                 }
                 .into());
diff --git a/rust/hg-core/src/errors.rs b/rust/hg-core/src/errors.rs
--- a/rust/hg-core/src/errors.rs
+++ b/rust/hg-core/src/errors.rs
@@ -81,7 +81,7 @@
                 write!(f, "abort: {}: {}", context, error)
             }
             HgError::CorruptedRepository(explanation) => {
-                write!(f, "abort: corrupted repository: {}", explanation)
+                write!(f, "abort: {}", explanation)
             }
             HgError::UnsupportedFeature(explanation) => {
                 write!(f, "unsupported feature: {}", explanation)
diff --git a/rust/hg-core/src/repo.rs b/rust/hg-core/src/repo.rs
--- a/rust/hg-core/src/repo.rs
+++ b/rust/hg-core/src/repo.rs
@@ -141,20 +141,22 @@
 
             if share_safe && !source_is_share_safe {
                 return Err(match config
-                    .get(b"safe-mismatch", b"source-not-safe")
+                    .get(b"share", b"safe-mismatch.source-not-safe")
                 {
                     Some(b"abort") | None => HgError::abort(
-                        "share source does not support share-safe requirement",
+                        "abort: share source does not support share-safe requirement\n\
+                        (see `hg help config.format.use-share-safe` for more information)",
                     ),
                     _ => HgError::unsupported("share-safe downgrade"),
                 }
                 .into());
             } else if source_is_share_safe && !share_safe {
                 return Err(
-                    match config.get(b"safe-mismatch", b"source-safe") {
+                    match config.get(b"share", b"safe-mismatch.source-safe") {
                         Some(b"abort") | None => HgError::abort(
-                            "version mismatch: source uses share-safe \
-                            functionality while the current share does not",
+                            "abort: version mismatch: source uses share-safe \
+                            functionality while the current share does not\n\
+                            (see `hg help config.format.use-share-safe` for more information)",
                         ),
                         _ => HgError::unsupported("share-safe upgrade"),
                     }
diff --git a/rust/rhg/src/error.rs b/rust/rhg/src/error.rs
--- a/rust/rhg/src/error.rs
+++ b/rust/rhg/src/error.rs
@@ -72,7 +72,7 @@
         match error {
             RepoError::NotFound { at } => CommandError::Abort {
                 message: format_bytes!(
-                    b"repository {} not found",
+                    b"abort: repository {} not found",
                     get_bytes_from_path(at)
                 ),
             },
diff --git a/tests/test-rhg.t b/tests/test-rhg.t
--- a/tests/test-rhg.t
+++ b/tests/test-rhg.t
@@ -187,7 +187,7 @@
 
   $ echo -e '\xFF' >> .hg/requires
   $ $NO_FALLBACK rhg debugrequirements
-  abort: corrupted repository: parse error in 'requires' file
+  abort: parse error in 'requires' file
   [255]
 
 Persistent nodemap