assert that the send message failed #727

Job	Run time
linux-shared-libs	2m 17s
linux-compiler-compat (clang-3)	2m 56s
clang-sanitizers (,thread)	2m 48s
linux-compiler-compat (clang-6)	3m 8s
linux-compat (manylinux2014-x64)	2m 18s
linux-compiler-compat (clang-8)	3m 46s
clang-sanitizers (,address,undefined)	3m 10s
linux-compat (manylinux2014-x86)	2m 18s
linux-compat (fedora-34-x64)	2m 10s
linux-compiler-compat (clang-9)	3m 31s
linux-compat (opensuse-leap)	3m 4s
linux-compiler-compat (clang-10)	3m 24s
linux-compat (rhel8-x64)	2m 23s
windows	4m 13s
linux-compiler-compat (clang-11)	3m 19s
linux-compat (al2-x64)	2m 6s
linux-compiler-compat (gcc-4.8)	2m 7s
windows-vc14 (x86)	2m 3s
linux-compiler-compat (gcc-5)	2m 26s
downstream	2m 32s
linux-compiler-compat (gcc-6)	2m 35s
windows-vc14 (x64)	5m 5s
linux-compiler-compat (gcc-7)	2m 19s
linux-compiler-compat (gcc-8)	2m 47s
windows-shared-libs	4m 14s
osx	3m 9s
	1h 16m 8s

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