[Bug?] pvlibDeprecationWarning and RuntimeWarnings invalid values

[SabineHaas]

When running the electricity sector example I get the following warnings. Just to be sure that you are aware of that @Piranias.

/home/sabine/virtualenvs/pvcompare/lib/python3.7/site-packages/pvlib/pvsystem.py:485: pvlibDeprecationWarning: temperature_model_parameters, racking_model, and module_type are not specified. Reverting to deprecated default: SAPM cell temperature model parameters for a glass/glass module in open racking. In v0.9, temperature_model_parameters or a valid combination of racking_model and module_type will be required.
  pvlibDeprecationWarning)
/home/sabine/virtualenvs/pvcompare/lib/python3.7/site-packages/pvlib/singlediode.py:520: RuntimeWarning: invalid value encountered in greater
  idx_p = 0. < Gsh
/home/sabine/virtualenvs/pvcompare/lib/python3.7/site-packages/pvlib/tools.py:304: RuntimeWarning: invalid value encountered in greater
  df['SW_Flag'] = df['f1'] > df['f2']
/home/sabine/virtualenvs/pvcompare/lib/python3.7/site-packages/pvlib/tools.py:311: RuntimeWarning: invalid value encountered in greater
  errflag = (abs(err) > .01).any()