Fatal Exception: NSGenericException
0  CoreFoundation                 0x183a2505c __exceptionPreprocess
1  libobjc.A.dylib                0x19bed5f64 objc_exception_throw
2  CFNetwork                      0x1841cb5a8 CFURLRequestSetRequestPriority
3  Wwwwww                         0x100704e9c __InstrumentDataTaskWithURLCompletionHandler_block_invoke + 234 (FPRNSURLSessionInstrument.m:234)
4  Wwwwww                         0x100704e9c __InstrumentDataTaskWithURLCompletionHandler_block_invoke + 234 (FPRNSURLSessionInstrument.m:234)
5  WwSwiftClient                  0x1015bdbc0 WwServer.dataRequest(_:completion:) + 279 (WwServer.swift:279)
6  WwSwiftClient                  0x1015baa24 WwServer.request<A>(_:completion:) + 223 (WwServer.swift:223)
7  Wwwwww                         0x10056ec3c specialized WwServerCacheOperation.execute() + 218 (WwServerCacheOperation.swift:218)
8  Wwwwww                         0x100582be4 partial apply for specialized closure #1 in WwServerCacheOperation.init(url:source:minimalLogging:resultCompletion:)
9  Wwwwww                         0x100620540 AsyncBlockOperation.start() + 85 (WwServerCacheOperation.swift:85)
10 Wwwwww                         0x10062059c @objc AsyncBlockOperation.start() (<compiler-generated>)
11 Foundation                     0x185206668 __NSOPERATIONQUEUE_IS_STARTING_AN_OPERATION__
12 Foundation                     0x185214720 __NSOQSchedule_f
13 libdispatch.dylib              0x1836a6600 _dispatch_block_async_invoke2
14 libdispatch.dylib              0x183697950 _dispatch_client_callout
15 libdispatch.dylib              0x18369ae04 _dispatch_continuation_pop
16 libdispatch.dylib              0x18369a460 _dispatch_async_redirect_invoke
17 libdispatch.dylib              0x1836a8f48 _dispatch_root_queue_drain
18 libdispatch.dylib              0x1836a9768 _dispatch_worker_thread2
19 libsystem_pthread.dylib        0x1f2975174 _pthread_wqthread
20 libsystem_pthread.dylib        0x1f2974f50 start_wqthread