Blocks-examples, float64 test is broken

[rizar]

See the test run.

After the tests finish, python crashes:

*** glibc detected *** /home/travis/miniconda/bin/python: free(): invalid pointer: 0x00007f539273e020 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x7da26)[0x7f539164ba26]
/home/travis/miniconda/bin/../lib/libpython3.4m.so.1.0(+0xc098e)[0x7f539236c98e]
/home/travis/miniconda/bin/../lib/libpython3.4m.so.1.0(+0x7be0f)[0x7f5392327e0f]
/home/travis/miniconda/bin/../lib/libpython3.4m.so.1.0(+0x91347)[0x7f539233d347]
/home/travis/miniconda/bin/../lib/libpython3.4m.so.1.0(+0xa2f0f)[0x7f539234ef0f]
/home/travis/miniconda/bin/../lib/libpython3.4m.so.1.0(+0xc4ac6)[0x7f5392370ac6]
/home/travis/miniconda/bin/../lib/libpython3.4m.so.1.0(+0x172b1c)[0x7f539241eb1c]
/home/travis/miniconda/bin/../lib/libpython3.4mhttps://github.com/mila-udem/blocks/pull/1150.so.1.0(_PyGC_CollectNoFail+0x2d)[0x7f539241f21d]
/home/travis/miniconda/bin/../lib/libpython3.4m.so.1.0(PyImport_Cleanup+0x113)[0x7f53923f3e23]
/home/travis/miniconda/bin/../lib/libpython3.4m.so.1.0(Py_Finalize+0x6e)[0x7f539240264e]
/home/travis/miniconda/bin/../lib/libpython3.4m.so.1.0(Py_Exit+0x8)[0x7f5392402788]
/home/travis/miniconda/bin/../lib/libpython3.4m.so.1.0(+0x156892)[0x7f5392402892]
/home/travis/miniconda/bin/../lib/libpython3.4m.so.1.0(PyErr_PrintEx+0x1d5)[0x7f5392402b55]
/home/travis/miniconda/bin/../lib/libpython3.4m.so.1.0(PyRun_SimpleFileExFlags+0x515)[0x7f5392403255]
/home/travis/miniconda/bin/../lib/libpython3.4m.so.1.0(Py_Main+0xba6)[0x7f539241d276]
/home/travis/miniconda/bin/python(main+0x15d)[0x400acd]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xed)[0x7f53915ef7ed]
/home/travis/miniconda/bin/python[0x4008a9]

This error reminds of similar issues that were recent fixed by @dwf in #1150