DOC: Update tutorial on error handling

Summary

The error handling has been updated in the tutorial (see #52 (closed)). Also, #49 (closed) has been fixed on the way.

Focus

src/doc/tutorials/erros.rst

Test Environment

make doc on top level and look at build/doc/html/tutorials/errors.html.

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src/doc/conf.py

@@ -43,6 +43,7 @@ release = '0.4.0-rc'
 # ones.
 extensions = [
     'sphinx.ext.autodoc',
+    'sphinx.ext.autosectionlabel',
     'sphinx.ext.intersphinx',
     'sphinx.ext.napoleon',     # For Google style docstrings
     "recommonmark",            # For markdown files.