Reduce nesting and remove extra whitespace in python_helper

Library/Homebrew/python_helper.rb

@@ -1,4 +1,3 @@
-
 # This is used in the Formula class when the user calls
 # `python`, `python2` or `python3`.
 
@@ -19,11 +18,12 @@ def python_helper(options={:allowed_major_versions => [2, 3]}, &block)
     # We are already inside of a `python do ... end` block, so just return
     # the current_python or false if the version.major is not allowed.
     if options[:allowed_major_versions].include?(@current_python.version.major)
-      @current_python
+      return @current_python
     else
-      false
+      return false
     end
-  else
+  end
+
   # Look for PythonInstalled requirements for this formula
   python_reqs = requirements.select{ |r| r.kind_of?(PythonInstalled) }
   if python_reqs.empty?
@@ -88,4 +88,3 @@ def python_helper(options={:allowed_major_versions => [2, 3]}, &block)
     end
   end
 end
-end  # enf of python_helper method