[ci skip] Add deprecation warnings to READMEs and CHANGES.txt

Author: bdbaddog

CHANGES.txt

@@ -8,7 +8,7 @@ NOTE: The 4.0.0 release of SCons dropped Python 2.7 support. Use 3.1.2 if
   Python 2.7 support is required (but note old SCons releases are unsupported).
 NOTE: Since SCons 4.3.0, Python 3.6.0 or above is required.
 NOTE: Since SCons 4.9.0, Python 3.7.0 or above is required.
-
+The last release to support Python 3.7 or Python 3.8 is NEXT_RELEASE.
 
 RELEASE  VERSION/DATE TO BE FILLED IN LATER
 

README-SF.rst

@@ -50,6 +50,7 @@ Execution Requirements
 Running SCons requires Python 3.7 or higher. There should be no other
 dependencies or requirements to run standard SCons.
 
+The last release to support Python 3.7 or Python 3.8 is NEXT_RELEASE.
 The last release to support Python 3.6 was 4.8.1.
 The last release to support Python 3.5 was 4.2.0.
 

README-local

@@ -46,9 +46,11 @@ EXECUTION REQUIREMENTS
 Running SCons requires Python 3.7 or higher. There should be no other
 dependencies or requirements to run standard SCons.
 
+The last release to support Python 3.7 or Python 3.8 is NEXT_RELEASE.
 The last release to support Python 3.6 was 4.8.1.
 The last release to support Python 3.5 was 4.2.0.
 
+
 The default SCons configuration assumes use of the Microsoft Visual C++
 compiler suite on WIN32 systems (either through the Visual Studio
 product, or through the separate Build Tools), and assumes a C compiler

README-package.rst

@@ -83,6 +83,7 @@ Execution Requirements
 Running SCons requires Python 3.7 or higher. There should be no other
 dependencies or requirements to run standard SCons.
 
+The last release to support Python 3.7 or Python 3.8 is NEXT_RELEASE.
 The last release to support Python 3.6 was 4.8.1.
 The last release to support Python 3.5 was 4.2.0.
 

README.rst

@@ -86,6 +86,7 @@ Execution Requirements
 Running SCons requires Python 3.7 or higher. There should be no other
 dependencies or requirements to run standard SCons.
 
+The last release to support Python 3.7 or Python 3.8 is NEXT_RELEASE.
 The last release to support Python 3.6 was 4.8.1.
 The last release to support Python 3.5 was 4.2.0.