fix pypi and sphinx urls

Author: videlec

README.rst

@@ -44,7 +44,8 @@ The available objects and functions from the `ppl` Python module are:
 Installation
 ------------
 
-The project is available at `Python Package Index <https://pypi.python.org/pypi/pplpy/>`_ and
+
+The project is available at `Python Package Index <https://pypi.org/project/pplpy/>`_ and
 can be installed with pip::
 
     $ pip install pplpy
@@ -76,7 +77,7 @@ Documentation
 
 An online version of the documentation is available at https://www.sagemath.org/pplpy/
 
-Compiling the html documentation requires make and `sphinx <http://www.sphinx-doc.org/en/master/>`_.
+Compiling the html documentation requires make and `sphinx <https://www.sphinx-doc.org/en/master/>`_.
 Before building the documentation, you need to install the pplpy package (sphinx uses Python introspection).
 The documentation source code is contained in the repository `docs` where there is a standard
 Makefile with a target `html`. Running `make html` in the `docs` repository builds the documentation
@@ -96,9 +97,9 @@ Requirements
 
 - `Cython <http://cython.org>`_ (tested with both 0.29 and 3.0)
 
-- `cysignals <https://pypi.python.org/pypi/cysignals>`_
+- `cysignals <https://pypi.org/project/cysignals/>`_
 
-- `gmpy2 <https://pypi.python.org/pypi/gmpy2>`_
+- `gmpy2 <https://pypi.org/project/gmpy2/>`_
 
 On Debian/Ubuntu systems the dependencies can be installed with::
 

docs/source/index.rst

@@ -6,7 +6,7 @@ Welcome to pplpy's documentation!
 Installation
 ------------
 
-pplpy is available from the `Python Package Index <https://pypi.python.org/pypi/pplpy/>`_. You can hence install it with::
+pplpy is available from the `Python Package Index <https://pypi.org/project/pplpy/>`_. You can hence install it with::
 
     $ pip install pplpy