Raise Errno::ENOENT instead of RuntimeError from Pathname#install

Library/Homebrew/extend/pathname.rb

@@ -35,6 +35,8 @@ class Pathname
   end
 
   def install_p src, new_basename = nil
+    raise Errno::ENOENT, src.to_s unless File.symlink?(src) || File.exist?(src)
+
     if new_basename
       new_basename = File.basename(new_basename) # rationale: see Pathname.+
       dst = self+new_basename
@@ -45,8 +47,6 @@ class Pathname
     src = src.to_s
     dst = dst.to_s
 
-    raise "#{src} does not exist" unless File.symlink? src or File.exist? src
-
     dst = yield(src, dst) if block_given?
 
     mkpath

Library/Homebrew/test/test_pathname.rb

@@ -83,9 +83,7 @@ class PathnameExtensionTests < Homebrew::TestCase
   end
 
   def test_install_missing_file
-    assert_raises(RuntimeError) do
-      @dst.install 'non_existent_file'
-    end
+    assert_raises(Errno::ENOENT) { @dst.install "non_existent_file" }
   end
 
   def test_install_removes_original