Merge pull request #34 from dxFeed/EN-2047-rtd-build-fix

En 2047 rtd build fix

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = 'dxfeed'
-version = '0.5.1'
+version = '0.5.2'
 description = 'DXFeed Python API via C API'
 authors = ['Index Management Team <[email protected]>']
 build = 'build.py'
@@ -38,6 +38,7 @@ toml = '^0.10.0'
 # Refer to: https://github.com/sdispater/poetry/issues/129
 # Issue to watch for: https://github.com/python-poetry/poetry/issues/1644
 jupyter = { version = '^1.0.0', optional = true }
+cython = { version = '^0.29.13', optional = true }
 
 [tool.poetry.dev-dependencies]
 cython = '^0.29.13'
@@ -48,7 +49,7 @@ sphinx_rtd_theme = '^0.4.3'
 pygments = '^2.6.1'
 
 [tool.poetry.extras]
-docs = ['jupyter']
+docs = ['jupyter', 'cython']
 
 [tool.taskipy.tasks]
 clear = 'find dxfeed/core -type f \( -iname *.c -o -iname *.cpp -o -iname *.pyd -o -iname *.so \) -delete'
@@ -60,5 +61,5 @@ post_build = 'task clear'
 post_test = 'task clear'
 
 [build-system]
-requires = ['poetry_core>=1.0.0', 'setuptools']
+requires = ['poetry_core>=1.0.0', 'setuptools', 'cython']
 build-backend = 'poetry.core.masonry.api'