Fix a bug occurring when n_samples in a class < n_features
Fix case n_sample in a class == 1
warning + log of prod -> sum of log
warning -> error
though we can check if reg_param > 0 and then use spherical covariance,
let's keep things simple
tests
ignore warnings, change docstring
BUG: only symmetrize matrix when it is not already symmetric
Merge pull request #4021 from jakevdp/fix_check_symmetric

BUG: only symmetrize matrix when it is not already symmetric
MAINT more informative assertion failure in test_common
Documentation of max depth parameter

Changed the docstring

Few docstring changes
Merge pull request #4026 from akshayah3/master

Documentation of max depth parameter in the DecisionTreeClassifier
remove deprecated ``n_bootstraps`` parameter in Bootstrap cv object, verbose in FactorAnalysis and SelectorMixin. Also adjust some deprecation strings.
remove deprecation tests.