api: add Error::JoinError

src/error.rs

@@ -59,16 +59,20 @@ pub enum Error {
     #[error(transparent)]
     FromUtf8Error(#[from] std::string::FromUtf8Error),
 
-    /// A non-specific [`io::Error`].
+    /// A generic [`io::Error`].
     #[error(transparent)]
     IoError(#[from] io::Error),
 
+    /// A [`tokio::task`] failed to execute to completion.
+    #[error(transparent)]
+    JoinError(#[from] tokio::task::JoinError),
+
     /// A [`Pm`](crate::pm::Pm) operation is not implemented.
     #[error("Operation `{op}` is unimplemented for `{pm}`")]
     #[allow(missing_docs)]
     OperationUnimplementedError { op: String, pm: String },
 
-    /// Miscellaneous other error.
+    /// An error from a non-specified category.
     #[error("{0}")]
     OtherError(String),
 }