Output of running, on NixOS 18.09, nix-shell -p gobjectIntrospection gtk3 'python37.withPackages(ps : with ps; [ matplotlib pygobject3 ipython ]), per the NixOS Wiki (https://nixos.wiki/wiki/Python#Gnome).

python3.7-hypothesis-3.66.2-test-failure.log

test_can_shrink_matrices_with_length_param passed 1 out of the required 3 times. Running test again until it passes 3 times.
test_can_shrink_matrices_with_length_param passed 2 out of the required 3 times. Running test again until it passes 3 times.
test_can_shrink_matrices_with_length_param passed 3 out of the required 3 times. Success!
test_can_time_out_in_simplify passed 1 out of the required 1 times. Success!
test_can_generate_interval_endpoints[0.0-1.0] passed 1 out of the required 1 times. Success!
test_can_generate_interval_endpoints[-1.0-0.0] passed 1 out of the required 1 times. Success!
test_can_generate_interval_endpoints[-2.2250738585072014e-308-2.2250738585072014e-308] passed 1 out of the required 1 times. Success!
test_half_bounded_generates_endpoint passed 1 out of the required 1 times. Success!
test_can_find_unique_lists_of_non_set_order passed 1 out of the required 1 times. Success!

===End Flaky Test Report===
========================== slowest 20 test durations ===========================
27.23s call     hypothesis-python/tests/cover/test_database_usage.py::test_trashes_invalid_examples
10.89s call     hypothesis-python/tests/cover/test_stateful.py::test_bad_machines_fail[RoseTreeStateMachine]
7.75s call     hypothesis-python/tests/cover/test_simple_collections.py::test_can_find_sets_unique_by_incomplete_data
7.29s call     hypothesis-python/tests/cover/test_database_usage.py::test_clears_out_everything_smaller_than_the_interesting_example
6.56s call     hypothesis-python/tests/cover/test_simple_collections.py::test_minimize_list_of_longish_lists
5.34s call     hypothesis-python/tests/cover/test_database_usage.py::test_clears_out_database_as_things_get_boring
4.29s call     hypothesis-python/tests/cover/test_deferred_strategies.py::test_large_branching_tree
4.28s call     hypothesis-python/tests/cover/test_stateful.py::test_removes_needless_steps
4.16s call     hypothesis-python/tests/cover/test_interleaving.py::test_can_eval_stream_inside_find
4.05s call     hypothesis-python/tests/cover/test_database_usage.py::test_respects_max_examples_in_database_usage
3.45s call     hypothesis-python/tests/cover/test_simple_strings.py::test_does_not_generate_surrogates
2.68s call     hypothesis-python/tests/cover/test_regex.py::test_negative_lookbehind
2.62s call     hypothesis-python/tests/cover/test_testdecorators.py::TestCases::test_float_addition_cancels
2.61s call     hypothesis-python/tests/cover/test_integer_ranges.py::test_intervals_shrink_to_center
2.58s call     hypothesis-python/tests/cover/test_testdecorators.py::test_contains_the_test_function_name_in_the_exception_string
2.50s call     hypothesis-python/tests/cover/test_regex.py::test_matching[True-True-\\s-None]
2.50s call     hypothesis-python/tests/cover/test_deferred_strategies.py::test_self_recursive_lists
2.34s call     hypothesis-python/tests/cover/test_regex.py::test_matching[True-True-\\w-is_word]
2.25s call     hypothesis-python/tests/cover/test_reusable_values.py::test_reusable_strategies_are_all_reusable
2.25s call     hypothesis-python/tests/cover/test_regex.py::test_matching[True-True-\\d-is_digit]
============= 46 failed, 1949 passed, 4 skipped in 556.42 seconds ==============
builder for '/nix/store/nbsllv0ycb2y6l96r6i9diid14g9j7d7-python3.7-hypothesis-3.66.2.drv' failed with exit code 1
cannot build derivation '/nix/store/w79pzg6vcyaijy810yn2lq4yz432k667-python3.7-chardet-3.0.4.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/6dkal43376zvw6379avifkky1xazg48x-python3.7-cryptography-2.3.1.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/k8cmqw0n4w0w1jy10rz65ffwa8qvy232-python3.7-requests-2.19.1.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/22902ljxwwbsnyrby3g7zhxbnd2445d7-python3.7-Sphinx-1.7.8.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/ma388i519l3w3vnzxmss44wc00nck111-python3.7-matplotlib-2.2.3.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/9zkxxx7iphv81mlyzk10vx4icsjkmz64-python3-3.7.1-env.drv': 1 dependencies couldn't be built
error: build of '/nix/store/9zkxxx7iphv81mlyzk10vx4icsjkmz64-python3-3.7.1-env.drv' failed