We actually require python 2.7

Fixes #30618

Author: steveklabnik

README.md

@@ -17,7 +17,7 @@ Read ["Installing Rust"] from [The Book].
 1. Make sure you have installed the dependencies:
 
    * `g++` 4.7 or `clang++` 3.x
-   * `python` 2.6 or later (but not 3.x)
+   * `python` 2.7 or later (but not 3.x)
    * GNU `make` 3.81 or later
    * `curl`
    * `git`