python: stop shadowing system python.

Use the `python2` etc. binaries instead and provide a link to `python`
in a directory not in the `PATH` by default.

Aliases/python2

@@ -0,0 +1 @@
+../Formula/python.rb

Aliases/python@2

@@ -0,0 +1 @@
+../Formula/python.rb

Formula/python.rb

@@ -3,6 +3,7 @@ class Python < Formula
   homepage "https://www.python.org"
   url "https://www.python.org/ftp/python/2.7.13/Python-2.7.13.tar.xz"
   sha256 "35d543986882f78261f97787fd3e06274bfa6df29fac9b4a94f73930ff98f731"
+  revision 1
   head "https://github.com/python/cpython.git", :branch => "2.7"
 
   bottle do
@@ -36,9 +37,6 @@ class Python < Formula
   depends_on "tcl-tk" => :optional
   depends_on "berkeley-db@4" => :optional
 
-  skip_clean "bin/pip", "bin/pip-2.7"
-  skip_clean "bin/easy_install", "bin/easy_install-2.7"
-
   resource "setuptools" do
     url "https://files.pythonhosted.org/packages/26/d1/dc7fe14ce4a3ff3faebf1ac11350de4104ea2d2a80c98393b55c84362b0c/setuptools-32.1.0.tar.gz"
     sha256 "86d57bf86edc0ecfd2dc0907ed3710bc4501fb13a06c0fcaf7632305b00ce832"
@@ -152,7 +150,7 @@ class Python < Formula
 
     # Allow python modules to use ctypes.find_library to find homebrew's stuff
     # even if homebrew is not a /usr/local/lib. Try this with:
-    # `brew install enchant && pip install pyenchant`
+    # `brew install enchant && pip2 install pyenchant`
     inreplace "./Lib/ctypes/macholib/dyld.py" do |f|
       f.gsub! "DEFAULT_LIBRARY_FALLBACK = [", "DEFAULT_LIBRARY_FALLBACK = [ '#{HOMEBREW_PREFIX}/lib',"
       f.gsub! "DEFAULT_FRAMEWORK_FALLBACK = [", "DEFAULT_FRAMEWORK_FALLBACK = [ '#{HOMEBREW_PREFIX}/Frameworks',"
@@ -218,6 +216,24 @@ class Python < Formula
         doc.install Dir["build/html/*"]
       end
     end
+
+    # Remove commands shadowing system python.
+    {
+      "2to3" => "2to3-2",
+      "easy_install" => "easy_install-2.7",
+      "idle" => "idle2",
+      "pip" => "pip2",
+      "pydoc" => "pydoc2",
+      "python" => "python2",
+      "python-config" => "python2-config",
+      "pythonw" => "pythonw2",
+      "smtpd.py" => "smtpd2.py",
+      "wheel" => nil,
+    }.each do |unversioned_name, versioned_name|
+      rm_f bin/unversioned_name
+      next unless versioned_name
+      (libexec/"bin").install_symlink bin/versioned_name => unversioned_name
+    end
   end
 
   def post_install
@@ -250,13 +266,13 @@ class Python < Formula
                   "--install-scripts=#{bin}",
                   "--install-lib=#{site_packages}"]
 
-    (libexec/"setuptools").cd { system "#{bin}/python", *setup_args }
-    (libexec/"pip").cd { system "#{bin}/python", *setup_args }
-    (libexec/"wheel").cd { system "#{bin}/python", *setup_args }
+    (libexec/"setuptools").cd { system "#{bin}/python2", *setup_args }
+    (libexec/"pip").cd { system "#{bin}/python2", *setup_args }
+    (libexec/"wheel").cd { system "#{bin}/python2", *setup_args }
 
     # When building from source, these symlinks will not exist, since
     # post_install happens after linking.
-    %w[pip pip2 pip2.7 easy_install easy_install-2.7 wheel].each do |e|
+    %w[pip2 pip2.7 easy_install-2.7].each do |e|
       (HOMEBREW_PREFIX/"bin").install_symlink bin/e
     end
 
@@ -336,11 +352,16 @@ class Python < Formula
   end
 
   def caveats; <<-EOS.undent
+    This formula installs a python2 executable to #{HOMEBREW_PREFIX}/bin.
+    If you wish to have this formula's python executable in your PATH then add
+    the following to #{shell_profile}:
+      export PATH="#{opt_libexec}/bin:$PATH"
+
     Pip and setuptools have been installed. To update them
-      pip install --upgrade pip setuptools
+      pip2 install --upgrade pip setuptools
 
     You can install Python packages with
-      pip install <package>
+      pip2 install <package>
 
     They will install into the site-package directory
       #{site_packages}
@@ -352,9 +373,9 @@ class Python < Formula
   test do
     # Check if sqlite is ok, because we build with --enable-loadable-sqlite-extensions
     # and it can occur that building sqlite silently fails if OSX's sqlite is used.
-    system "#{bin}/python", "-c", "import sqlite3"
+    system "#{bin}/python2", "-c", "import sqlite3"
     # Check if some other modules import. Then the linked libs are working.
-    system "#{bin}/python", "-c", "import Tkinter; root = Tkinter.Tk()"
-    system bin/"pip", "list"
+    system "#{bin}/python2", "-c", "import Tkinter; root = Tkinter.Tk()"
+    system bin/"pip2", "list"
   end
 end