try

Cargo.toml

@@ -54,6 +54,7 @@ tee = "0.1"
 tempfile = "3"
 typenum = "1"
 url = "2"
+which = "7"
 
 [dependencies.bstr]
 version = "1"

src/hg_connect_stdio.rs

@@ -231,6 +231,17 @@ pub fn get_stdio_connection(url: &Url, flags: c_int) -> Option<Box<dyn HgRepo>>
         path.as_os_str().as_bytes().to_owned()
     };
     let path = CString::new(path).unwrap();
+    warn!(target: "root", "{:?}", which::which("hg"));
+    if let Ok(hg) = which::which("hg") {
+        use bstr::ByteSlice;
+        let output = std::process::Command::new(hg).arg("--version").output().unwrap();
+        warn!(target: "root", "{}", output.stdout.as_bstr());
+        warn!(target: "root", "{}", output.stderr.as_bstr());
+
+        let output = std::process::Command::new("/bin/sh").args(["-x", "-c", "hg --version"]).output().unwrap();
+        warn!(target: "root", "{}", output.stdout.as_bstr());
+        warn!(target: "root", "{}", output.stderr.as_bstr());
+    }
     let proc = unsafe {
         hg_connect_stdio(
             userhost.as_ref().map_or(ptr::null(), |s| s.as_ptr()),