pyqt5: use Language::Python.

Library/Formula/pyqt5.rb

@@ -10,13 +10,7 @@ class Pyqt5 < Formula
   depends_on :python3 => :recommended
   depends_on :python => :optional
 
-  if !Formula["python"].installed? && build.with?("python") &&
-     build.with?("python3")
-    odie <<-EOS.undent
-      pyqt5: You cannot use system Python 2 and Homebrew's Python 3 simultaneously.
-      Either `brew install python` or use `--without-python3`.
-    EOS
-  elsif build.without?("python3") && build.without?("python")
+  if build.without?("python3") && build.without?("python")
     odie "pyqt5: --with-python3 must be specified when using --without-python"
   end
 
@@ -28,18 +22,8 @@ class Pyqt5 < Formula
     depends_on 'sip'
   end
 
-  def pythons
-    pythons = []
-    ["python", "python3"].each do |python|
-      next if build.without? python
-      version = /\d\.\d/.match `#{python} --version 2>&1`
-      pythons << [python, version]
-    end
-    pythons
-  end
-
   def install
-    pythons.each do |python, version|
+    Language::Python.each_python(build) do |python, version|
       args = [ "--confirm-license",
                "--bindir=#{bin}",
                "--destdir=#{lib}/python#{version}/site-packages",
@@ -57,14 +41,14 @@ def install
       system python, "configure.py", *args
       system "make"
       system "make", "install"
-      system "make", "clean" if pythons.length > 1
+      system "make", "clean"
     end
   end
 
   test do
     system "pyuic5", "--version"
     system "pylupdate5", "-version"
-    pythons.each do |python, version|
+    Language::Python.each_python(build) do |python, version|
       system python, "-c", "import PyQt5"
     end
   end