LL : correction of two code-blocks python -> pycon after suggestion from #1424 and command grep -r 'code-block:: python' -A 3 ..

Author: LLyaudet

source/tutorials/installing-packages.rst

@@ -52,7 +52,7 @@ please install the latest 3.x version from `python.org`_ or refer to the
 
 .. Note:: If you're a newcomer and you get an error like this:
 
-    .. code-block:: python
+    .. code-block:: pycon
 
         >>> python3 --version
         Traceback (most recent call last):

source/tutorials/packaging-projects.rst

@@ -493,7 +493,7 @@ Make sure you're still in your virtual environment, then run Python:
 
 and import the package:
 
-.. code-block:: python
+.. code-block:: pycon
 
     >>> from example_package_YOUR_USERNAME_HERE import example
     >>> example.add_one(2)