deb: fix bug in find_dsc_file

src/context/schroot.rs

@@ -262,4 +262,14 @@ impl ContextDriver for SchrootDriver {
         }
         Ok(())
     }
+
+    fn exists(&self, path: &Path) -> io::Result<bool> {
+        let status = self.run(
+            "test",
+            &["-e".to_string(), path.to_string_lossy().to_string()],
+            &[],
+            None,
+        )?;
+        Ok(status.success())
+    }
 }