[V3] Remove all mentions of Python 3.5 (#1896)

We don't speak of him any more.

.github/CONTRIBUTING.md

@@ -31,7 +31,7 @@ We love receiving contributions from our community. Any assistance you can provi
 # 2. Ground Rules
 We've made a point to use [ZenHub](https://www.zenhub.com/) (a plugin for GitHub) as our main source of collaboration and coordination. Your experience contributing to Red will be greatly improved if you go get that plugin.
 1. Ensure cross compatibility for Windows, Mac OS and Linux.
-2. Ensure all Python features used in contributions exist and work in Python 3.5 and above.
+2. Ensure all Python features used in contributions exist and work in Python 3.6 and above.
 3. Create new tests for code you add or bugs you fix. It helps us help you by making sure we don't accidentally break anything :grinning:
 4. Create any issues for new features you'd like to implement and explain why this feature is useful to everyone and not just you personally.
 5. Don't add new cogs unless specifically given approval in an issue discussing said cog idea.
@@ -79,7 +79,7 @@ Note: If you haven't used `pipenv` before but are comfortable with virtualenvs,
 We've recently started using [tox](https://github.com/tox-dev/tox) to run all of our tests. It's extremely simple to use, and if you followed the previous section correctly, it is already installed to your virtual environment.
 
 Currently, tox does the following, creating its own virtual environments for each stage:
-- Runs all of our unit tests with [pytest](https://github.com/pytest-dev/pytest) on both python 3.5 and 3.6 (test environments `py35` and `py36` respectively)
+- Runs all of our unit tests with [pytest](https://github.com/pytest-dev/pytest) on python 3.6 (test environment `py36`)
 - Ensures documentation builds without warnings, and all hyperlinks have a valid destination (test environment `docs`)
 - Ensures that the code meets our style guide with [black](https://github.com/ambv/black) (test environment `style`)
 
@@ -94,8 +94,6 @@ Our style checker of choice, [black](https://github.com/ambv/black), actually ha
 
 Use the command `black --help` to see how to use this tool. The full style guide is explained in detail on [black's GitHub repository](https://github.com/ambv/black). **There is one exception to this**, however, which is that we set the line length to 99, instead of black's default 88. When using `black` on the command line, simply use it like so: `black -l 99 <src>`.
 
-Note: Python 3.6+ is required to install and run black. If you installed your development environment with Python 3.5, black will not be installed.
-
 ### 4.4 Make
 You may have noticed we have a `Makefile` and a `make.bat` in the top-level directory. For now, you can do two things with them:
 1. `make reformat`: Reformat all python files in the project with Black

docs/guide_cog_creation.rst

@@ -17,8 +17,7 @@ you in the process.
 Getting started
 ---------------
 
-To start off, be sure that you have installed Python 3.5 or higher (if you
+To start off, be sure that you have installed Python 3.6 or higher. Open a terminal or command prompt and type
-are on Windows, stick with 3.5). Open a terminal or command prompt and type
 :code:`pip install --process-dependency-links -U git+https://github.com/Cog-Creators/Red-DiscordBot@V3/develop#egg=redbot[test]`
 (note that if you get an error with this, try again but put :code:`python -m` in front of the command
 This will install the latest version of V3.

redbot/__init__.py

@@ -12,12 +12,3 @@ if discord.version_info.major < 1:
         " >= 1.0.0."
     )
     sys.exit(1)
-
-if sys.version_info < (3, 6, 0):
-    print(Back.RED + "[DEPRECATION WARNING]")
-    print(
-        Back.RED + "You are currently running Python 3.5."
-        " Support for Python 3.5 will end with the release of beta 16."
-        " Please update your environment to Python 3.6 as soon as possible to avoid"
-        " any interruptions after the beta 16 release."
-    )

redbot/launcher.py

@@ -25,7 +25,7 @@ from redbot.core.cli import confirm
 if sys.platform == "linux":
     import distro
 
-PYTHON_OK = sys.version_info >= (3, 5)
+PYTHON_OK = sys.version_info >= (3, 6)
 INTERACTIVE_MODE = not len(sys.argv) > 1  # CLI flags = non-interactive
 
 INTRO = "==========================\nRed Discord Bot - Launcher\n==========================\n"
@@ -472,7 +472,7 @@ def main_menu():
 def main():
     if not PYTHON_OK:
         raise RuntimeError(
-            "Red requires Python 3.5 or greater. Please install the correct version!"
+            "Red requires Python 3.6 or greater. Please install the correct version!"
         )
     if args.debuginfo:  # Check first since the function triggers an exit
         debug_info()