thread 'main' panicked at 'called `Result::unwrap()

I am getting this error intermittently, not sure where to debug this.

The code(taken from examples and https://github.com/cholcombe973/ceph_usage/blob/master/src/lib.rs) is here:

https://github.com/SachinMaharana/ceph-op/blob/449ab8ac38dc737919f68ef77e4aa2579bf84581/src/main.rs

```
cargo run
Finished dev [unoptimized + debuginfo] target(s) in 0.03s
Running `target/debug/ceph-op`
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Utf8Error { valid_up_to: 10, error_len: Some(1) }', /home/centos/.cargo/registry/src/github.com-1ecc6299db9ec823/ceph-3.0.0/src/ceph.rs:1988:46
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```