CI: Unexpected `PGRES_FATAL_ERROR` in tests

[TylerLoewen]

Error in Julia 1.0 Ubuntu job: https://github.com/invenia/LibPQ.jl/runs/3577583027?check_suite_focus=true

Example SELECT: Test Failed at /home/runner/work/LibPQ.jl/LibPQ.jl/test/runtests.jl:159
  Expression: status(result) == (LibPQ.libpq_c).PGRES_TUPLES_OK
   Evaluated: PGRES_FATAL_ERROR::ExecStatusType = 7 == PGRES_TUPLES_OK::ExecStatusType = 2
Stacktrace:
 [1] macro expansion at /home/runner/work/LibPQ.jl/LibPQ.jl/test/runtests.jl:159 [inlined]
 [2] macro expansion at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Test/src/Test.jl:1083 [inlined]
 [3] macro expansion at /home/runner/work/LibPQ.jl/LibPQ.jl/test/runtests.jl:75 [inlined]
 [4] macro expansion at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Test/src/Test.jl:1083 [inlined]
 [5] macro expansion at /home/runner/work/LibPQ.jl/LibPQ.jl/test/runtests.jl:72 [inlined]
 [6] macro expansion at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Test/src/Test.jl:1083 [inlined]
 [7] top-level scope at /home/runner/work/LibPQ.jl/LibPQ.jl/test/runtests.jl:36