cli: more explicit error message when rad node logs fail — heartwood

If the rad node is spawned by systemd there won’t be any logs file to read and rad node logs command will fail with the standard error message from fs.

 use std::io::{BufRead, BufReader, Read, Seek, SeekFrom};
 use std::{fs, io, path::Path, process, thread, time};
 use anyhow::anyhow;
 use anyhow::{anyhow, Context};
 use localtime::LocalTime;
 use radicle::node;

 }
 pub fn logs(lines: usize, follow: Option<time::Duration>, profile: &Profile) -> anyhow::Result<()> {
     let logs = profile.home.node().join("node.log");
     let logs_path = profile.home.node().join("node.log");
     let mut file = File::open(logs_path.clone())
         .map(BufReader::new)
         .with_context(|| format!("Failed to read logs from file {}. Did you start
 the node with 'rad node start'? If radicle node is run through a process manager,
 check out logs using the manager's tool.", logs_path.display()))?;
     let mut file = BufReader::new(File::open(logs)?);
     file.seek(SeekFrom::End(0))?;
     let mut tail = Vec::new();