Revert "python_requirement: fix ENV for python3"

This reverts commit 85271644b0083cbc0fd6fea71120d1ad859fbc2a.

Alex noticed that setting PYTHONPATH causes weirdness if we depend_on
something which may be optionally built --with-python3; PYTHONPATH
unexpectedly contains python3 modules in the depending formula if
the formula upon which it depends was built --with-python3 even
though the depending formula may only use python2.

Closes Homebrew/homebrew#43724. Closes Homebrew/homebrew#43744.

1 files changed, 3 insertions, 5 deletions

diff --git a/Library/Homebrew/requirements/python_requirement.rb b/Library/Homebrew/requirements/python_requirement.rb
index d4e4a116d..f41722782 100644
--- a/Library/Homebrew/requirements/python_requirement.rb
+++ b/Library/Homebrew/requirements/python_requirement.rb
@@ -24,7 +24,9 @@ class PythonRequirement < Requirement
       ENV.prepend_path "PATH", Formula["python"].opt_bin
     end
 
-    ENV["PYTHONPATH"] = "#{HOMEBREW_PREFIX}/lib/python#{short_version}/site-packages"
+    if python_binary == "python"
+      ENV["PYTHONPATH"] = "#{HOMEBREW_PREFIX}/lib/python#{short_version}/site-packages"
+    end
   end
 
   def python_short_version
@@ -60,10 +62,6 @@ class Python3Requirement < PythonRequirement
 
   satisfy(:build_env => false) { which_python }
 
-  env do
-    ENV["PYTHONPATH"] = "#{HOMEBREW_PREFIX}/lib/python#{python_short_version}/site-packages"
-  end
-
   def python_binary
     "python3"
   end