mock-io shows random stack traces for non running futures tasks

[itissid]

This may not be so much of a bug as much as an annoyance in my builds. To be sure my tests always pass and on random occasions the call to is_async() during read() causes the following stack trace to be also printed in the test result output:

thread 'test::test_empty' panicked at 'no Task is currently running', libcore/option.rs:1010:5
stack backtrace:
   0:        0x1033b965f - std::sys::unix::backtrace::tracing::imp::unwind_backtrace::he14a7566b
dd4ad59
                               at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1:        0x1033adacd - std::sys_common::backtrace::print::h1a7b3835c923145c
                               at libstd/sys_common/backtrace.rs:71
                               at libstd/sys_common/backtrace.rs:59
   2:        0x1033bc6c3 - std::panicking::default_hook::{{closure}}::hf3ce01776f699802
                               at libstd/panicking.rs:211
   3:        0x1033bc44c - std::panicking::default_hook::h3c82163ec405ace2
                               at libstd/panicking.rs:227
   4:        0x1033bcdf7 - <std::panicking::begin_panic::PanicPayload<A> as core::panic::BoxMeUp
>::get::h171c0508ba0f257d
                               at libstd/panicking.rs:476
   5:        0x1033bc95c - std::panicking::continue_panic_fmt::h99ced5a4f2cb7fe1
                               at libstd/panicking.rs:390
   6:        0x1033bc848 - std::panicking::try::do_call::h227895fcedff86c1
                               at libstd/panicking.rs:325
   7:        0x1033f9981 - core::ptr::drop_in_place::h4911d68bde261059
                               at libcore/panicking.rs:77
   8:        0x1033f99f8 - core::ptr::drop_in_place::h4911d68bde261059
                               at libcore/option.rs:1010
   9:        0x10322f4ae - futures::task_impl::core::is_get_ptr::he9f1821c3b760147
                               at libcore/option.rs:322
  10:        0x10322d53d - core::sync::atomic::fence::hfe8e9abb8e00ad51
                               at /Users/sidharth/.cargo/registry/src/github.com-1ecc6299db9ec82
3/futures-0.1.25/src/task_impl/mod.rs:43
  11:        0x10322d6c3 - core::sync::atomic::fence::hfe8e9abb8e00ad51
                               at /Users/sidharth/.cargo/registry/src/github.com-1ecc6299db9ec82
3/futures-0.1.25/src/task_impl/mod.rs:115
  12:        0x10320a8d3 - mock_io::tokio::is_task_ctx::{{closure}}::h5833a77e05b3a583
                               at /Users/sidharth/.cargo/git/checkouts/mock-io-4da294547111861b/
f3ddbf1/src/lib.rs:494
  13:        0x1032095ad - core::ptr::drop_in_place::hf9eeaa83057de510
                               at libstd/panicking.rs:310
  14:        0x1033c8f5e - panic_unwind::dwarf::eh::read_encoded_pointer::hc34cd1841a9c3448
                               at libpanic_unwind/lib.rs:102
  15:        0x103209488 - core::ptr::drop_in_place::hf9eeaa83057de510
                               at libstd/panicking.rs:289
  16:        0x10320c0a3 - alloc::alloc::realloc::h925ba350de2998bc
                               at libstd/panic.rs:392
  17:        0x10320a80f - mock_io::tokio::is_task_ctx::h1fc02f6b020dea65
                               at /Users/sidharth/.cargo/git/checkouts/mock-io-4da294547111861b/
f3ddbf1/src/lib.rs:494
  18:        0x10320668d - mock_io::Mock::is_async::hb4e16b2b11688e96
                               at /Users/sidharth/.cargo/git/checkouts/mock-io-4da294547111861b/
f3ddbf1/src/lib.rs:193
  19:        0x103206b2a - mock_io::Inner::action::hb2a7c897c61e0b3f
                               at /Users/sidharth/.cargo/git/checkouts/mock-io-4da294547111861b/
f3ddbf1/src/lib.rs:307
  20:        0x10323c142 - kaleidoscope_rust::lexer::LexerUtils::is_valid_number::h013ea4e0eef20
77f
                               at src/lexer.rs:96
  21:        0x1031c3033 - lexer::test::test_empty::ha383491365942f77
                               at tests/lexer.rs:56
  22:        0x1031c3aa0 - lexer::test::test_empty::{{closure}}::h20d79d1f71ed6f75
                               at tests/lexer.rs:53
  23:        0x1031c12b0 - core::ops::function::FnOnce::call_once::h197155977faf18fd
                               at libcore/ops/function.rs:238
  24:        0x1031c54c1 - <F as alloc::boxed::FnBox<A>>::call_box::h3bcc9ca146dc16c0
                               at libtest/lib.rs:1468
                               at libcore/ops/function.rs:238
                               at liballoc/boxed.rs:672
  25:        0x1033c8f5e - panic_unwind::dwarf::eh::read_encoded_pointer::hc34cd1841a9c3448
                               at libpanic_unwind/lib.rs:102
  26:        0x1031e5d6c - std::sys_common::backtrace::__rust_begin_short_backtrace::h7a1f954d1c
2e46dd
                               at libstd/panicking.rs:289
                               at libstd/panic.rs:392
                               at libtest/lib.rs:1423
                               at libstd/sys_common/backtrace.rs:136
  27:        0x1031e6827 - std::panicking::try::do_call::h117606c4744e3cbc
                               at libstd/thread/mod.rs:409
                               at libstd/panic.rs:313
                               at libstd/panicking.rs:310
  28:        0x1033c8f5e - panic_unwind::dwarf::eh::read_encoded_pointer::hc34cd1841a9c3448
                               at libpanic_unwind/lib.rs:102
  29:        0x1031d3a54 - <F as alloc::boxed::FnBox<A>>::call_box::h7e8a9f097e3dc7dc
                               at libstd/panicking.rs:289
                               at libstd/panic.rs:392
                               at libstd/thread/mod.rs:408
                               at liballoc/boxed.rs:672
  30:        0x1033ab35b - std::sys::unix::thread::Thread::new::thread_start::hd0450e633b3bea88
                               at liballoc/boxed.rs:682
                               at libstd/sys_common/thread.rs:24
                               at libstd/sys/unix/thread.rs:90
  31:     0x7fff97b74059 - _pthread_body
  32:     0x7fff97b73fd6 - _pthread_start

A cursory reading lead me to believe that the framework is trying to detect if there is a future task which produces this panic. There is a warning there in that doc saying that calling this outside a poll(Future::poll, I think?) is dangerous. It seems that a code change is warranted but I am not sure I understand how to implement it.