diff --git a/docs/dev/virtualenvs.rst b/docs/dev/virtualenvs.rst
index b4591e43b..fe6bd3f9e 100644
--- a/docs/dev/virtualenvs.rst
+++ b/docs/dev/virtualenvs.rst
@@ -156,7 +156,7 @@ when you share your project with others. You should get output similar to this
     Adding requests to Pipfile's [packages]...
     P.S. You have excellent taste! ✨ 🍰 ✨
 
-.. _Requests: http://docs.python-requests.org/en/master/
+.. _Requests: https://requests.readthedocs.io/en/latest/
 
 
 Using installed packages
diff --git a/docs/scenarios/admin.rst b/docs/scenarios/admin.rst
index 07d263945..f6433c213 100644
--- a/docs/scenarios/admin.rst
+++ b/docs/scenarios/admin.rst
@@ -155,44 +155,42 @@ tests (net, CPU) fail, it will send an email.
     # Package for email services:
     import smtplib
     import string
-    MAX_NET_USAGE = 400000
+    MAX_NET_USAGE = 400000 # bytes per seconds
     MAX_ATTACKS = 4
     attack = 0
-    counter = 0
     while attack <= MAX_ATTACKS:
         sleep(4)
-        counter = counter + 1
-        # Check the cpu usage
-        if cpu_percent(interval = 1) > 70:
-            attack = attack + 1
-        # Check the net usage
-        neti1 = net_io_counters()[1]
-        neto1 = net_io_counters()[0]
+
+        # Check the net usage wit named tuples
+        neti1 = net_io_counters().bytes_recv
+        neto1 = net_io_counters().bytes_sent
         sleep(1)
-        neti2 = net_io_counters()[1]
-        neto2 = net_io_counters()[0]
+        neti2 = net_io_counters().bytes_recv
+        neto2 = net_io_counters().bytes_sent
+
         # Calculate the bytes per second
         net = ((neti2+neto2) - (neti1+neto1))/2
-        if net > MAX_NET_USAGE:
-            attack = attack + 1
-        if counter > 25:
-            attack = 0
-            counter = 0
+
+        # Check the net and cpu usage
+        if (net > MAX_NET_USAGE) or (cpu_percent(interval = 1) > 70):
+            attack+=1
+        elif attack > 1:
+            attack-=1
+    
     # Write a very important email if attack is higher than 4
     TO = "you@your_email.com"
     FROM = "webmaster@your_domain.com"
     SUBJECT = "Your domain is out of system resources!"
     text = "Go and fix your server!"
-    BODY = string.join(("From: %s" %FROM,"To: %s" %TO,"Subject: %s" %SUBJECT, "",text), "\r\n")
+    string="\r\n"
+    BODY = string.join(("From: %s" %FROM,"To: %s" %TO,
+                        "Subject: %s" %SUBJECT, "",text))
     server = smtplib.SMTP('127.0.0.1')
     server.sendmail(FROM, [TO], BODY)
     server.quit()
 
 
-A full terminal application like a widely extended top which is based on
-psutil and with the ability of a client-server monitoring is
-`glance <https://github.com/nicolargo/glances/>`_.
-
+A full terminal application like a widely extended top is `Glance <https://github.com/nicolargo/glances/>`_, which is based on psutil and has the ability for client-server monitoring.
 
 *******
 Ansible
@@ -397,17 +395,3 @@ up. Buildout is primarily used to download and set up dependencies in `Python
 eggs <https://stackoverflow.com/questions/2051192/what-is-a-python-egg>`_
 format of the software being developed or deployed. Recipes for build tasks in
 any environment can be created, and many are already available.
-
-
-*******
-Shinken
-*******
-
-`Shinken <http://www.shinken-monitoring.org/>`_ is a modern, Nagios compatible
-monitoring framework written in Python. Its main goal is to give users a flexible
-architecture for their monitoring system that is designed to scale to large
-environments.
-
-Shinken is backwards-compatible with the Nagios configuration standard and
-plugins. It works on any operating system and architecture that supports Python,
-which includes Windows, Linux, and FreeBSD.
diff --git a/docs/scenarios/client.rst b/docs/scenarios/client.rst
index 1457fa479..c2d5c289b 100644
--- a/docs/scenarios/client.rst
+++ b/docs/scenarios/client.rst
@@ -28,7 +28,7 @@ your URLs, or to form-encode your POST data. Keep-alive and HTTP connection
 pooling are 100% automatic, powered by urllib3, which is embedded within
 Requests.
 
-- `Documentation <http://docs.python-requests.org/en/latest/index.html>`_
+- `Documentation <https://requests.readthedocs.io/en/latest/>`_
 - `PyPi <http://pypi.org/project/requests>`_
 - `GitHub <https://github.com/kennethreitz/requests>`_
 
diff --git a/docs/scenarios/imaging.rst b/docs/scenarios/imaging.rst
index 7b0e71935..8fe7e08fe 100644
--- a/docs/scenarios/imaging.rst
+++ b/docs/scenarios/imaging.rst
@@ -62,7 +62,7 @@ Example
     exif_data
 
 There are more examples of the Pillow library in the
-`Pillow tutorial <https://pillow.readthedocs.io/en/3.0.x/handbook/tutorial.html>`_.
+`Pillow tutorial <https://pillow.readthedocs.io/en/stable/handbook/tutorial.html>`_.
 
 
 ***************************
@@ -109,4 +109,4 @@ Example
 
 There are more Python-implemented examples of OpenCV in this `collection of
 tutorials
-<https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_tutorials.html>`_.
+<https://opencv-tutorial.readthedocs.io/en/latest/>`_.
diff --git a/docs/scenarios/scrape.rst b/docs/scenarios/scrape.rst
index 54747b295..527719200 100644
--- a/docs/scenarios/scrape.rst
+++ b/docs/scenarios/scrape.rst
@@ -28,7 +28,7 @@ lxml and Requests
 `lxml <http://lxml.de/>`_ is a pretty extensive library written for parsing
 XML and HTML documents very quickly, even handling messed up tags in the
 process. We will also be using the
-`Requests <http://docs.python-requests.org/en/latest/>`_ module instead of the
+`Requests <https://requests.readthedocs.io/en/latest/>`_ module instead of the
 already built-in urllib2 module due to improvements in speed and readability.
 You can easily install both using ``pip install lxml`` and
 ``pip install requests``.
diff --git a/docs/scenarios/xml.rst b/docs/scenarios/xml.rst
index 3bdf15b6c..24dab5869 100644
--- a/docs/scenarios/xml.rst
+++ b/docs/scenarios/xml.rst
@@ -81,3 +81,30 @@ and then you can access elements, attributes, and values like this:
 xmltodict also lets you roundtrip back to XML with the unparse function,
 has a streaming mode suitable for handling files that don't fit in memory,
 and supports XML namespaces.
+
+**********
+xmlschema
+**********
+
+`xmlschema <https://github.com/sissaschool/xmlschema>`_ provides support for using XSD-Schemas in Python.
+Unlike other XML libraries, automatic type parsing is available, so f.e. if the schema defines an element to be of type ``int``, the parsed ``dict`` will contain also an ``int`` value for that element. 
+Moreover the library supports automatic and explicit validation of XML documents against a schema.
+
+.. code-block:: python
+
+    from xmlschema import XMLSchema, etree_tostring
+
+    # load a XSD schema file
+    schema = XMLSchema("your_schema.xsd")
+    
+    # validate against the schema
+    schema.validate("your_file.xml")
+    
+    # or
+    schema.is_valid("your_file.xml")
+    
+    # decode a file
+    data = schmema.decode("your_file.xml")
+    
+    # encode to string
+    s = etree_tostring(schema.encode(data))
diff --git a/docs/starting/install/osx.rst b/docs/starting/install/osx.rst
index d0aa601aa..4a8a8e03b 100644
--- a/docs/starting/install/osx.rst
+++ b/docs/starting/install/osx.rst
@@ -10,9 +10,10 @@ Installing Python 2 on Mac OS X
 .. note::
     Check out our :ref:`guide for installing Python 3 on OS X<install3-osx>`.
 
-**Mac OS X comes with Python 2.7 out of the box.**
+**Mac OS X comes with Python 2.7 out of the box between versions 10.8 and 12.3.**
 
-You do not need to install or configure anything else to use Python. Having said
+If your Mac OS X version is between the above versions,
+you do not need to install or configure anything else to use Python. Having said
 that, I would strongly recommend that you install the tools and libraries
 described in the next section before you start building Python applications for
 real-world use. In particular, you should always install Setuptools, as it makes
diff --git a/docs/starting/install3/osx.rst b/docs/starting/install3/osx.rst
index 37252d615..fa90fb93a 100644
--- a/docs/starting/install3/osx.rst
+++ b/docs/starting/install3/osx.rst
@@ -9,9 +9,10 @@ Installing Python 3 on Mac OS X
 
 .. image:: /_static/photos/34435689480_2e6f358510_k_d.jpg
 
-**Mac OS X comes with Python 2.7 out of the box.**
+**Mac OS X comes with Python 2.7 out of the box between versions 10.8 and 12.3.**
 
-You do not need to install or configure anything else to use Python 2. These
+If your Mac OS X version is between the above versions,
+you do not need to install or configure anything else to use Python 2. These
 instructions document the installation of Python 3.
 
 The version of Python that ships with OS X is great for learning, but it's not
diff --git a/docs/writing/reading.rst b/docs/writing/reading.rst
index ad67ea3cb..1e03a4def 100644
--- a/docs/writing/reading.rst
+++ b/docs/writing/reading.rst
@@ -43,7 +43,7 @@ reading. Each one of these projects is a paragon of Python coding.
   Requests is an Apache2 Licensed HTTP library, written in Python,
   for human beings.
 
-- `Tablib <https://github.com/kennethreitz/tablib>`_
+- `Tablib <https://github.com/jazzband/tablib>`_
   Tablib is a format-agnostic tabular dataset library, written in Python.
 
 
diff --git a/docs/writing/style.rst b/docs/writing/style.rst
index 9858112de..d8c096a05 100644
--- a/docs/writing/style.rst
+++ b/docs/writing/style.rst
@@ -465,8 +465,7 @@ easy-to-read version of PEP 8 is also available at `pep8.org <http://pep8.org/>`
 
 This is highly recommended reading. The entire Python community does their
 best to adhere to the guidelines laid out within this document. Some project
-may sway from it from time to time, while others may
-`amend its recommendations <http://docs.python-requests.org/en/master/dev/contributing/#kenneth-reitz-s-code-style>`_.
+may sway from it from time to time, while others may amend its recommendations.
 
 That being said, conforming your Python code to PEP 8 is generally a good idea
 and helps make code more consistent when working on projects with other
diff --git a/runtime.txt b/runtime.txt
index 5a958026d..cc1923a40 100644
--- a/runtime.txt
+++ b/runtime.txt
@@ -1 +1 @@
-3.5
+3.8