pythons: update caveats

Closes Homebrew/homebrew#37528. Closes Homebrew/homebrew#37527. Closes Homebrew/homebrew#37530. Closes Homebrew/homebrew#37529.

Signed-off-by: Tim D. Smith <git@tim-smith.us>

Formula/pypy.rb

@@ -128,7 +128,7 @@ class Pypy < Formula
     Setuptools and pip have been installed, so you can use easy_install_pypy and
     pip_pypy.
     To update setuptools and pip between pypy releases, run:
-        #{scripts_folder}/pip install --upgrade setuptools
+        pip_pypy install --upgrade pip setuptools
 
     See: https://github.com/Homebrew/homebrew/blob/master/share/doc/homebrew/Homebrew-and-Python.md
     EOS

Formula/pypy3.rb

@@ -113,8 +113,8 @@ class Pypy3 < Formula
 
     Setuptools and pip have been installed, so you can use easy_install_pypy3 and
     pip_pypy3.
-    To update setuptools and pip between pypy3 releases, run:
-        #{scripts_folder}/pip install --upgrade setuptools pip
+    To update pip and setuptools between pypy3 releases, run:
+        pip_pypy3 install --upgrade pip setuptools
 
     See: https://github.com/Homebrew/homebrew/blob/master/share/doc/homebrew/Homebrew-and-Python.md
     EOS

Formula/python.rb

@@ -281,9 +281,8 @@ class Python < Formula
   end
 
   def caveats; <<-EOS.undent
-    Setuptools and pip have been installed. To update them
-      pip install --upgrade setuptools
-      pip install --upgrade pip
+    Pip and setuptools have been installed. To update them
+      pip install --upgrade pip setuptools
 
     You can install Python packages with
       pip install <package>

Formula/python3.rb

@@ -275,8 +275,8 @@ class Python3 < Formula
 
   def caveats
     text = <<-EOS.undent
-      Pip has been installed. To update it
-        pip3 install --upgrade pip
+      Pip and setuptools have been installed. To update them
+        pip3 install --upgrade pip setuptools
 
       You can install Python packages with
         pip3 install <package>