Remove Sphinx version duplication

The version specified in the documentation is provided by the Sphinx config in `docs/conf.py`.

This duplicates the version specified in `hazelcast/init.py`, and previously [became outdated](#690).

Unfortunately, in this PR I updated the version incorrectly (i.e. to `5.4.0`, not `5.5.0`), highlighting the issues with duplicating this data.

Instead, we should have a single place the version if specified, and reference it in the Sphinx config.

Example output following this change:

In addition, while trying to build the documents locally, `make html` failed with a cryptic error message:
> *** commands commence before first target. Stop.

I didn't have Sphinx installed, and while `make` was happy to evaluate the `if` check for it's existence, printing an error message was disallowed outside of a target. Fixed by adding a target, and requiring that on any Sphinx related targets.
This can be tested by updating the `SPHINXBUILD` command to something that doesn't exist and trying to build the documentation:
> % make html
Makefile:13: *** The 'non-existant-sphinx-build' command was not found. Make sure you have Sphinx installed, then set the SPHINXBUILD environment variable to point to the full path of the 'non-existant-sphinx-build' executable. Alternatively you can add the directory with the executable to your PATH. If you don\'t have Sphinx installed, grab it from http://sphinx-doc.org/.  Stop.

docs/Makefile

@@ -3,11 +3,12 @@
 
 # You can set these variables from the command line.
 SPHINXOPTS    =
-SPHINXBUILD   = sphinx-build
+SPHINXBUILD   = non-existant-sphinx-build
 PAPER         =
 BUILDDIR      = _build
 
-# User-friendly check for sphinx-build
+.PHONY: check-sphinx
+check-sphinx:
 ifeq ($(shell which $(SPHINXBUILD) >/dev/null 2>&1; echo $$?), 1)
 	$(error The '$(SPHINXBUILD)' command was not found. Make sure you have Sphinx installed, then set the SPHINXBUILD environment variable to point to the full path of the '$(SPHINXBUILD)' executable. Alternatively you can add the directory with the executable to your PATH. If you don\'t have Sphinx installed, grab it from http://sphinx-doc.org/)
 endif
@@ -54,44 +55,44 @@ clean:
 	rm -rf $(BUILDDIR)/*
 
 .PHONY: html
-html:
+html: check-sphinx
 	$(SPHINXBUILD) -b html $(ALLSPHINXOPTS) $(BUILDDIR)/html
 	@echo
 	@echo "Build finished. The HTML pages are in $(BUILDDIR)/html."
 
 .PHONY: dirhtml
-dirhtml:
+dirhtml: check-sphinx
 	$(SPHINXBUILD) -b dirhtml $(ALLSPHINXOPTS) $(BUILDDIR)/dirhtml
 	@echo
 	@echo "Build finished. The HTML pages are in $(BUILDDIR)/dirhtml."
 
 .PHONY: singlehtml
-singlehtml:
+singlehtml: check-sphinx
 	$(SPHINXBUILD) -b singlehtml $(ALLSPHINXOPTS) $(BUILDDIR)/singlehtml
 	@echo
 	@echo "Build finished. The HTML page is in $(BUILDDIR)/singlehtml."
 
 .PHONY: pickle
-pickle:
+pickle: check-sphinx
 	$(SPHINXBUILD) -b pickle $(ALLSPHINXOPTS) $(BUILDDIR)/pickle
 	@echo
 	@echo "Build finished; now you can process the pickle files."
 
 .PHONY: json
-json:
+json: check-sphinx
 	$(SPHINXBUILD) -b json $(ALLSPHINXOPTS) $(BUILDDIR)/json
 	@echo
 	@echo "Build finished; now you can process the JSON files."
 
 .PHONY: htmlhelp
-htmlhelp:
+htmlhelp: check-sphinx
 	$(SPHINXBUILD) -b htmlhelp $(ALLSPHINXOPTS) $(BUILDDIR)/htmlhelp
 	@echo
 	@echo "Build finished; now you can run HTML Help Workshop with the" \
 	      ".hhp project file in $(BUILDDIR)/htmlhelp."
 
 .PHONY: qthelp
-qthelp:
+qthelp: check-sphinx
 	$(SPHINXBUILD) -b qthelp $(ALLSPHINXOPTS) $(BUILDDIR)/qthelp
 	@echo
 	@echo "Build finished; now you can run "qcollectiongenerator" with the" \
@@ -101,7 +102,7 @@ qthelp:
 	@echo "# assistant -collectionFile $(BUILDDIR)/qthelp/HazelcastPythonClient.qhc"
 
 .PHONY: applehelp
-applehelp:
+applehelp: check-sphinx
 	$(SPHINXBUILD) -b applehelp $(ALLSPHINXOPTS) $(BUILDDIR)/applehelp
 	@echo
 	@echo "Build finished. The help book is in $(BUILDDIR)/applehelp."
@@ -110,7 +111,7 @@ applehelp:
 	      "bundle."
 
 .PHONY: devhelp
-devhelp:
+devhelp: check-sphinx
 	$(SPHINXBUILD) -b devhelp $(ALLSPHINXOPTS) $(BUILDDIR)/devhelp
 	@echo
 	@echo "Build finished."
@@ -120,111 +121,111 @@ devhelp:
 	@echo "# devhelp"
 
 .PHONY: epub
-epub:
+epub: check-sphinx
 	$(SPHINXBUILD) -b epub $(ALLSPHINXOPTS) $(BUILDDIR)/epub
 	@echo
 	@echo "Build finished. The epub file is in $(BUILDDIR)/epub."
 
 .PHONY: epub3
-epub3:
+epub3: check-sphinx
 	$(SPHINXBUILD) -b epub3 $(ALLSPHINXOPTS) $(BUILDDIR)/epub3
 	@echo
 	@echo "Build finished. The epub3 file is in $(BUILDDIR)/epub3."
 
 .PHONY: latex
-latex:
+latex: check-sphinx
 	$(SPHINXBUILD) -b latex $(ALLSPHINXOPTS) $(BUILDDIR)/latex
 	@echo
 	@echo "Build finished; the LaTeX files are in $(BUILDDIR)/latex."
 	@echo "Run \`make' in that directory to run these through (pdf)latex" \
 	      "(use \`make latexpdf' here to do that automatically)."
 
 .PHONY: latexpdf
-latexpdf:
+latexpdf: check-sphinx
 	$(SPHINXBUILD) -b latex $(ALLSPHINXOPTS) $(BUILDDIR)/latex
 	@echo "Running LaTeX files through pdflatex..."
 	$(MAKE) -C $(BUILDDIR)/latex all-pdf
 	@echo "pdflatex finished; the PDF files are in $(BUILDDIR)/latex."
 
 .PHONY: latexpdfja
-latexpdfja:
+latexpdfja: check-sphinx
 	$(SPHINXBUILD) -b latex $(ALLSPHINXOPTS) $(BUILDDIR)/latex
 	@echo "Running LaTeX files through platex and dvipdfmx..."
 	$(MAKE) -C $(BUILDDIR)/latex all-pdf-ja
 	@echo "pdflatex finished; the PDF files are in $(BUILDDIR)/latex."
 
 .PHONY: text
-text:
+text: check-sphinx
 	$(SPHINXBUILD) -b text $(ALLSPHINXOPTS) $(BUILDDIR)/text
 	@echo
 	@echo "Build finished. The text files are in $(BUILDDIR)/text."
 
 .PHONY: man
-man:
+man: check-sphinx
 	$(SPHINXBUILD) -b man $(ALLSPHINXOPTS) $(BUILDDIR)/man
 	@echo
 	@echo "Build finished. The manual pages are in $(BUILDDIR)/man."
 
 .PHONY: texinfo
-texinfo:
+texinfo: check-sphinx
 	$(SPHINXBUILD) -b texinfo $(ALLSPHINXOPTS) $(BUILDDIR)/texinfo
 	@echo
 	@echo "Build finished. The Texinfo files are in $(BUILDDIR)/texinfo."
 	@echo "Run \`make' in that directory to run these through makeinfo" \
 	      "(use \`make info' here to do that automatically)."
 
 .PHONY: info
-info:
+info: check-sphinx
 	$(SPHINXBUILD) -b texinfo $(ALLSPHINXOPTS) $(BUILDDIR)/texinfo
 	@echo "Running Texinfo files through makeinfo..."
 	make -C $(BUILDDIR)/texinfo info
 	@echo "makeinfo finished; the Info files are in $(BUILDDIR)/texinfo."
 
 .PHONY: gettext
-gettext:
+gettext: check-sphinx
 	$(SPHINXBUILD) -b gettext $(I18NSPHINXOPTS) $(BUILDDIR)/locale
 	@echo
 	@echo "Build finished. The message catalogs are in $(BUILDDIR)/locale."
 
 .PHONY: changes
-changes:
+changes: check-sphinx
 	$(SPHINXBUILD) -b changes $(ALLSPHINXOPTS) $(BUILDDIR)/changes
 	@echo
 	@echo "The overview file is in $(BUILDDIR)/changes."
 
 .PHONY: linkcheck
-linkcheck:
+linkcheck: check-sphinx
 	$(SPHINXBUILD) -b linkcheck $(ALLSPHINXOPTS) $(BUILDDIR)/linkcheck
 	@echo
 	@echo "Link check complete; look for any errors in the above output " \
 	      "or in $(BUILDDIR)/linkcheck/output.txt."
 
 .PHONY: doctest
-doctest:
+doctest: check-sphinx
 	$(SPHINXBUILD) -b doctest $(ALLSPHINXOPTS) $(BUILDDIR)/doctest
 	@echo "Testing of doctests in the sources finished, look at the " \
 	      "results in $(BUILDDIR)/doctest/output.txt."
 
 .PHONY: coverage
-coverage:
+coverage: check-sphinx
 	$(SPHINXBUILD) -b coverage $(ALLSPHINXOPTS) $(BUILDDIR)/coverage
 	@echo "Testing of coverage in the sources finished, look at the " \
 	      "results in $(BUILDDIR)/coverage/python.txt."
 
 .PHONY: xml
-xml:
+xml: check-sphinx
 	$(SPHINXBUILD) -b xml $(ALLSPHINXOPTS) $(BUILDDIR)/xml
 	@echo
 	@echo "Build finished. The XML files are in $(BUILDDIR)/xml."
 
 .PHONY: pseudoxml
-pseudoxml:
+pseudoxml: check-sphinx
 	$(SPHINXBUILD) -b pseudoxml $(ALLSPHINXOPTS) $(BUILDDIR)/pseudoxml
 	@echo
 	@echo "Build finished. The pseudo-XML files are in $(BUILDDIR)/pseudoxml."
 
 .PHONY: dummy
-dummy:
+dummy: check-sphinx
 	$(SPHINXBUILD) -b dummy $(ALLSPHINXOPTS) $(BUILDDIR)/dummy
 	@echo
 	@echo "Build finished. Dummy builder generates no files."

docs/conf.py

@@ -20,6 +20,8 @@
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 sys.path.insert(0, os.path.abspath(".."))
 
+from hazelcast import __version__
+
 # -- General configuration ------------------------------------------------
 
 # If your documentation needs a minimal Sphinx version, state it here.
@@ -72,9 +74,9 @@
 # built documents.
 #
 # The short X.Y version.
-version = "5.4.0"
+version = __version__
 # The full version, including alpha/beta/rc tags.
-release = "5.4.0"
+release = version
 
 autodoc_member_order = "bysource"
 autoclass_content = "both"