feat: understandable error message when accounts.lock can't be locked

Author: Hocuri

deltachat-rpc-server/src/main.rs

@@ -30,7 +30,7 @@ async fn main() {
     // thread, and it is impossible to cancel that read. This can make shutdown of the runtime hang
     // until the user presses enter."
     if let Err(error) = &r {
-        log::error!("Fatal error: {error:#}.")
+        log::error!("Error: {error:#}.")
     }
     std::process::exit(if r.is_ok() { 0 } else { 1 });
 }

src/accounts.rs

@@ -4,7 +4,7 @@ use std::collections::BTreeMap;
 use std::future::Future;
 use std::path::{Path, PathBuf};
 
-use anyhow::{ensure, Context as _, Result};
+use anyhow::{bail, ensure, Context as _, Result};
 use futures::stream::FuturesUnordered;
 use futures::StreamExt;
 use serde::{Deserialize, Serialize};
@@ -73,9 +73,7 @@ impl Accounts {
         let config_file = dir.join(CONFIG_NAME);
         ensure!(config_file.exists(), "{:?} does not exist", config_file);
 
-        let config = Config::from_file(config_file, writable)
-            .await
-            .context("failed to load accounts config")?;
+        let config = Config::from_file(config_file, writable).await?;
         let events = Events::new();
         let stockstrings = StockStrings::new();
         let push_subscriber = PushSubscriber::new();
@@ -480,7 +478,9 @@ impl Config {
             };
             return Ok(cfg);
         }
-        let lock_task = Self::create_lock_task(dir.to_path_buf()).await?;
+        let Ok(lock_task) = Self::create_lock_task(dir.to_path_buf()).await else {
+            bail!("Delta Chat is already running. To use Delta Chat, you must first close the existing Delta Chat process, or restart your device.\n\n(accounts.lock file is already locked)");
+        };
         let cfg = Self {
             file,
             inner,