Tests failure on macOS

[Luthaf]

Building the latest master (db2e2445d34c196c94731249061740123f9fbc28) on macOS (with a small change to fix #378), I get a errors for this test: https://github.com/cosmo-epfl/librascal/blob/db2e2445d34c196c94731249061740123f9fbc28/tests/test_calculator.cc#L290-L357

Running 37 test cases...
/Users/guillaume/code/librascal/tests/test_calculator.cc:331: error: in "representation_test/multiple_center_mask_test<rascal__CalculatorFixture<rascal__MultipleStructureSphericalCovariants<rascal__MultipleStructureManagerNLCCStrictFixtureCenterMask>>>": check rep_full.cols() == rep_no_center.cols() has failed [180 != 160]
/Users/guillaume/code/librascal/tests/test_calculator.cc:346: error: in "representation_test/multiple_center_mask_test<rascal__CalculatorFixture<rascal__MultipleStructureSphericalCovariants<rascal__MultipleStructureManagerNLCCStrictFixtureCenterMask>>>": check diff <= math::DBL_FTOL has failed [1.2293360728836216 > 2.2204460492503131e-14]
/Users/guillaume/code/librascal/tests/test_calculator.cc:331: error: in "representation_test/multiple_center_mask_test<rascal__CalculatorFixture<rascal__MultipleStructureSphericalCovariants<rascal__MultipleStructureManagerNLCCStrictFixtureCenterMask>>>": check rep_full.cols() == rep_no_center.cols() has failed [1080 != 960]
/Users/guillaume/code/librascal/tests/test_calculator.cc:346: error: in "representation_test/multiple_center_mask_test<rascal__CalculatorFixture<rascal__MultipleStructureSphericalCovariants<rascal__MultipleStructureManagerNLCCStrictFixtureCenterMask>>>": check diff <= math::DBL_FTOL has failed [0.64030837310064947 > 2.2204460492503131e-14]
/Users/guillaume/code/librascal/tests/test_calculator.cc:331: error: in "representation_test/multiple_center_mask_test<rascal__CalculatorFixture<rascal__MultipleStructureSphericalCovariants<rascal__MultipleStructureManagerNLCCStrictFixtureCenterMask>>>": check rep_full.cols() == rep_no_center.cols() has failed [180 != 160]
/Users/guillaume/code/librascal/tests/test_calculator.cc:346: error: in "representation_test/multiple_center_mask_test<rascal__CalculatorFixture<rascal__MultipleStructureSphericalCovariants<rascal__MultipleStructureManagerNLCCStrictFixtureCenterMask>>>": check diff <= math::DBL_FTOL has failed [1.2238504980765332 > 2.2204460492503131e-14]
/Users/guillaume/code/librascal/tests/test_calculator.cc:331: error: in "representation_test/multiple_center_mask_test<rascal__CalculatorFixture<rascal__MultipleStructureSphericalCovariants<rascal__MultipleStructureManagerNLCCStrictFixtureCenterMask>>>": check rep_full.cols() == rep_no_center.cols() has failed [1080 != 960]
/Users/guillaume/code/librascal/tests/test_calculator.cc:346: error: in "representation_test/multiple_center_mask_test<rascal__CalculatorFixture<rascal__MultipleStructureSphericalCovariants<rascal__MultipleStructureManagerNLCCStrictFixtureCenterMask>>>": check diff <= math::DBL_FTOL has failed [0.80292449399458199 > 2.2204460492503131e-14]

*** 8 failures are detected in the test module "boost_test_sequence"