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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• All automated tests pass
• Reference related Issues
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  • Intent of new code
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Check List for the Reviewer

• I understand the intent of this MR
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CHANGELOG.md

@@ -31,20 +31,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [0.5.1] - 2021-02-12 ##
 
-### Added ###
-
-### Changed ###
-
-### Deprecated ###
-
-### Removed ###
-
 ### Fixed ###
 
 * #43 - Error with `execute_query` when server doesn't support query caching.
 
-### Security ###
-
 ## [0.5.0] - 2021-02-11 ##
 
 ### Added ###
@@ -77,18 +67,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   `QueryNotUniqueError` if no or more than one possible candidate is
   found, respectively.
 
-### Deprecated ###
-
 ### Removed ###
 
 * Dynamic exception type `EntityMultiError`. 
 * `get_something` functions from all error object in `exceptions.py`
 * `AmbiguityException`
 
-### Fixed ###
-
-### Security ###
-
 ## [0.4.1] - 2021-02-10 ##
 
 ### Added ###
@@ -98,18 +82,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   entity.
 * Automated documentation builds: `make doc`
 
-### Changed ###
-
-### Deprecated ###
-
-### Removed ###
-
 ### Fixed ###
 
 * deepcopy of `_Messages` objects
 
-### Security ###
-
 ## [0.4.0] - 2020-07-17##
 
 ### Added ###