statsmodels.formula.api importError: cannot import name 'TimeSeries'

Upgrading statsmodels worked for me,

pip install statsmodels --upgrade

For python3:

You need to upgrade statsmodels. If that is a problem go for a specific version such as:

py -m pip install statsmodels==0.6.0

Then you can use

py -m pip install statsmodels --upgrade

For python2.x

pip install statsmodels --upgrade