accounts: work around non-immediate closing of sql connections

When removing an account, try 5 times with 1 second sleep in between
in case removal of database files fails. This happens on Windows
platform sometimes due to a known bug in r2d2 [1].

[1] sfackler/r2d2#99

src/accounts.rs

@@ -148,9 +148,27 @@ impl Accounts {
         drop(ctx);
 
         if let Some(cfg) = self.config.get_account(id).await {
-            fs::remove_dir_all(async_std::path::PathBuf::from(&cfg.dir))
-                .await
-                .context("failed to remove account data")?;
+            let mut counter = 0;
+            loop {
+                counter += 1;
+
+                if let Err(err) = fs::remove_dir_all(async_std::path::PathBuf::from(&cfg.dir))
+                    .await
+                    .context("failed to remove account data")
+                {
+                    // Spend up to 1 minute trying to remove the files.
+                    // Files may remain locked up to 30 seconds due to r2d2 bug:
+                    // https://github.com/sfackler/r2d2/issues/99
+                    if counter > 60 {
+                        return Err(err);
+                    }
+
+                    // Wait 1 second and try again.
+                    async_std::task::sleep(std::time::Duration::from_millis(1000)).await;
+                } else {
+                    break;
+                }
+            }
         }
         self.config.remove_account(id).await?;