When importing tensorflow, I get the following error: No module named 'numpy.core._multiarray_umath'
I also had the same issue. It got resloved once i upgraded the numpy from 1.15.4 to 1.16.1.
If you're using pip:
pip install numpy --upgrade
Numpy that came with Anaconda3 is of version 1.15.4. so i upgraded and it worked.
Side note: if you're also using scikit-image in your script, be aware that numpy 1.16.3 has a conflict with old versions of scikit-image (e.g. you may get
ImportError: cannot import name '_validate_lengths'). In that case,
pip install --upgrade scikit-image from terminal solved the issue for me.
Hope it helps!!