make the error message clearer when running distroless containers (#13549)

Previously you could get a confusing error message like this:

```
$ docker run ghcr.io/astral-sh/uv run python
error: Could not read ELF interpreter from any of the following paths: /bin/sh, /usr/bin/env, /bin/dash, /bin/ls
```

Now the error message is better:

```
error: Failed to discover managed Python installations
  Caused by: Failed to determine the libc used on the current platform
  Caused by: Failed to find any common binaries to determine libc from: /bin/sh, /usr/bin/env, /bin/dash, /bin/ls
```

See https://github.com/astral-sh/uv/issues/8635.

---------

Co-authored-by: konsti <konstin@mailbox.org>
Co-authored-by: Zanie Blue <contact@zanie.dev>

crates/uv-python/src/discovery.rs

@@ -222,8 +222,9 @@ pub enum Error {
         PythonSource,
     ),
 
-    /// An error was encountered when interacting with a managed Python installation.
-    #[error(transparent)]
+    /// An error was encountered while trying to find a managed Python installation matching the
+    /// current platform.
+    #[error("Failed to discover managed Python installations")]
     ManagedPython(#[from] crate::managed::Error),
 
     /// An error was encountered when inspecting a virtual environment.

crates/uv-python/src/downloads.rs

@@ -91,7 +91,7 @@ pub enum Error {
     NoDownloadFound(PythonDownloadRequest),
     #[error("A mirror was provided via `{0}`, but the URL does not match the expected format: {0}")]
     Mirror(&'static str, &'static str),
-    #[error(transparent)]
+    #[error("Failed to determine the libc used on the current platform")]
     LibcDetection(#[from] LibcDetectionError),
     #[error("Remote Python downloads JSON is not yet supported, please use a local path")]
     RemoteJSONNotSupported,

crates/uv-python/src/libc.rs

@@ -37,6 +37,8 @@ pub enum LibcDetectionError {
     InvalidLdSoOutputMusl(PathBuf),
     #[error("Could not read ELF interpreter from any of the following paths: {0}")]
     CoreBinaryParsing(String),
+    #[error("Failed to find any common binaries to determine libc from: {0}")]
+    NoCommonBinariesFound(String),
     #[error("Failed to determine libc")]
     Io(#[from] io::Error),
 }
@@ -207,12 +209,24 @@ fn find_ld_path() -> Result<PathBuf, LibcDetectionError> {
     // See: https://github.com/astral-sh/uv/issues/1810
     // See: https://github.com/astral-sh/uv/issues/4242#issuecomment-2306164449
     let attempts = ["/bin/sh", "/usr/bin/env", "/bin/dash", "/bin/ls"];
+    let mut found_anything = false;
     for path in attempts {
-        if let Some(ld_path) = find_ld_path_at(path) {
-            return Ok(ld_path);
+        if std::fs::exists(path).ok() == Some(true) {
+            found_anything = true;
+            if let Some(ld_path) = find_ld_path_at(path) {
+                return Ok(ld_path);
+            }
         }
     }
-    Err(LibcDetectionError::CoreBinaryParsing(attempts.join(", ")))
+    let attempts_string = attempts.join(", ");
+    if !found_anything {
+        // Known failure cases here include running the distroless Docker images directly
+        // (depending on what subcommand you use) and certain Nix setups. See:
+        // https://github.com/astral-sh/uv/issues/8635
+        Err(LibcDetectionError::NoCommonBinariesFound(attempts_string))
+    } else {
+        Err(LibcDetectionError::CoreBinaryParsing(attempts_string))
+    }
 }
 
 /// Attempt to find the path to the `ld` executable by

crates/uv-python/src/managed.rs

@@ -87,7 +87,7 @@ pub enum Error {
     AbsolutePath(PathBuf, #[source] io::Error),
     #[error(transparent)]
     NameParseError(#[from] installation::PythonInstallationKeyError),
-    #[error(transparent)]
+    #[error("Failed to determine the libc used on the current platform")]
     LibcDetection(#[from] LibcDetectionError),
     #[error(transparent)]
     MacOsDylib(#[from] macos_dylib::Error),