return false from #piping? when $stdout is not an IO.

lib/pry/repl.rb

@@ -219,7 +219,8 @@ class Pry
     #   # `piping?` returns `true`
     #   % pry | tee log
     def piping?
-      !($stdout.respond_to?(:tty?) and $stdout.tty?) && $stdin.tty? && !Pry::Helpers::BaseHelpers.windows?
+      return false unless $stdout.respond_to?(:tty?)
+      !$stdout.tty? && $stdin.tty? && !Pry::Helpers::BaseHelpers.windows?
     end
 
     # @return [void]

spec/pry_repl_spec.rb

@@ -1,6 +1,5 @@
 require_relative 'helper'
-
-describe "The whole thing" do
+describe Pry::REPL do
   it "should let you run commands in the middle of multiline expressions" do
     ReplTester.start do
       input  'def a'
@@ -112,4 +111,14 @@ describe "The whole thing" do
       end
     end
   end
+
+  describe "#piping?" do
+    it "returns false when $stdout is a non-IO object" do
+      repl = described_class.new(Pry.new, {})
+      old_stdout = $stdout
+      $stdout = Class.new { def write(*) end }.new
+      expect(repl.send(:piping?)).to eq(false)
+      $stdout = old_stdout
+    end
+  end
 end