Clarify Python 3.5 is the minimum supported version in the installati…

…on section. (pytorch#41937)

Summary: Pull Request resolved: pytorch#41937

Reviewed By: izdeby

Differential Revision: D22702924

Pulled By: mrshenli

fbshipit-source-id: 67306435e80f80236b585f1d5406444daec782d6

README.md

@@ -149,7 +149,7 @@ They require JetPack 4.2 and above, and [@dusty-nv](https://github.com/dusty-nv)
 
 ### From Source
 
-If you are installing from source, you will need a C++14 compiler. Also, we highly recommend installing an [Anaconda](https://www.anaconda.com/distribution/#download-section) environment.
+If you are installing from source, you will need Python 3.6 or later and a C++14 compiler. Also, we highly recommend installing an [Anaconda](https://www.anaconda.com/distribution/#download-section) environment.
 You will get a high-quality BLAS library (MKL) and you get controlled dependency versions regardless of your Linux distro.
 
 Once you have [Anaconda](https://www.anaconda.com/distribution/#download-section) installed, here are the instructions.
@@ -221,7 +221,7 @@ NVTX is a part of CUDA distributive, where it is called "Nsight Compute". To ins
 Be sure that CUDA with Nsight Compute is installed after Visual Studio 2017.
 
 Currently VS 2017, VS 2019 and Ninja are supported as the generator of CMake. If `ninja.exe` is detected in `PATH`, then Ninja will be used as the default generator, otherwise it will use VS 2017.
-<br/> If Ninja is selected as the generator, the latest MSVC which is newer than VS 2015 (14.0) will get selected as the underlying toolchain if you have Python > 3.5, otherwise VS 2015 will be selected so you'll have to activate the environment. If you use CMake <= 3.14.2 and has VS 2019 installed, then even if you specify VS 2017 as the generator, VS 2019 will get selected as the generator.
+<br/> If Ninja is selected as the generator, the latest MSVC which is newer than VS 2015 (14.0) will get selected as the underlying toolchain. If you use CMake <= 3.14.2 and has VS 2019 installed, then even if you specify VS 2017 as the generator, VS 2019 will get selected as the generator.
 
 CUDA and MSVC have strong version dependencies, so even if you use VS 2017 / 2019, you will get build errors like `nvcc fatal : Host compiler targets unsupported OS`. For this kind of problem, please install the corresponding VS toolchain in the table below and then you can either specify the toolset during activation (recommended) or set `CUDAHOSTCXX` to override the cuda host compiler (not recommended if there are big version differences).