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- ThreadSanitizer helps to detect races and some memory errors,
- AddressSanitizer helps to detect memory errors,
- Python debug builds help to detect e.g reference counting errors.

Adding all those tools to testing coverage discovers e.g. the following
bugs (not a full list):

---- 8< ----

py27-thread-tsan:
WARNING: ThreadSanitizer: data race (pid=7143)
  Write of size 8 at 0x7b1400000650 by main thread:
    #0 free ../../../../src/libsanitizer/tsan/tsan_interceptors.cc:649 (libtsan.so.0+0x2b46a)
    #1 free ../../../../src/libsanitizer/tsan/tsan_interceptors.cc:643 (libtsan.so.0+0x2b46a)
    #2 golang::_chan::decref() golang/runtime/libgolang.cpp:470 (liblibgolang.so.0.1+0x47f2)
    #3 _chanxdecref golang/runtime/libgolang.cpp:452 (liblibgolang.so.0.1+0x484a)
    #4 _test_go_c golang/runtime/libgolang_test_c.c:86 (_golang_test.so+0x13a2e)
    #5 __pyx_pf_6golang_12_golang_test_12test_go_c golang/_golang_test.cpp:3340 (_golang_test.so+0xcbaa...