500 for DELETE project: Directory not empty

[myieye]

We got a 500 on a run of SendNewProject_Big:

fail: Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware[1]
      => TraceId:9a5a2c749311107d53f078ce230ad42e => ConnectionId:0HN32P1PMPNCS => RequestPath:/api/project/767c16a8-d7c9-4eff-9274-0f7ca15e04d1 RequestId:0HN32P1PMPNCS:00000015
      An unhandled exception has occurred while executing the request.
      System.IO.IOException: Directory not empty : '/hg-repos/s/send-new-project-767c16a8-dev-flex/.hg/store/data/_anthropology'
         at System.IO.FileSystem.RemoveDirectoryRecursive(String fullPath)
         at LexBoxApi.Services.HgService.<>c__DisplayClass11_0.<DeleteRepo>b__0() in /LexBoxApi/Services/HgService.cs:line 80
         at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
      --- End of stack trace from previous location ---
         at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
         at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
      --- End of stack trace from previous location ---
         at LexBoxApi.Services.HgService.DeleteRepo(String code) in /LexBoxApi/Services/HgService.cs:line 80
         at LexBoxApi.Controllers.ProjectController.DeleteProject(Guid id) in /LexBoxApi/Controllers/ProjectController.cs:line 172
         at lambda_method1355(Closure, Object)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.AwaitableObjectResultExecutor.Execute(ActionContext actionContext, IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Logged|12_1(ControllerActionInvoker invoker)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeInnerFilterAsync>g__Awaited|13_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|20_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
         at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|7_0(Endpoint endpoint, Task requestTask, ILogger logger)
         at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
         at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
         at LexSyncReverseProxy.ProxyKernel.<>c.<<UseResumableStatusHack>b__4_0>d.MoveNext() in /SyncReverseProxy/ProxyKernel.cs:line 135
      --- End of stack trace from previous location ---
         at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
         at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
         at Microsoft.AspNetCore.HttpLogging.HttpLoggingMiddleware.InvokeInternal(HttpContext context, HttpLoggingOptions options, HttpLoggingAttribute loggingAttribute, HttpLoggingFields loggingFields)
         at Microsoft.AspNetCore.HttpLogging.HttpLoggingMiddleware.InvokeInternal(HttpContext context, HttpLoggingOptions options, HttpLoggingAttribute loggingAttribute, HttpLoggingFields loggingFields)
         at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddlewareImpl.<Invoke>g__Awaited|10_0(ExceptionHandlerMiddlewareImpl middleware, HttpContext context, Task task)

[rmunn]

Looks like a similar error as #486, where it was "System.IO.IOException: Directory not empty : '/hg-repos/kevin-test-01/.hg/store/data'". Might or might not be a duplicate, as the root cause might be different.