Fixes #436 - memory write regression (#437)

* Fix regression made in #432

*This situation pushes me more and more to work on tests engine*

* Fix eX memory write on Python 2

As string literal is unicode, in Py2 the code below would fail if `bytestr` is just a `str`, due to `'0'` being unocide literal:

```
bytestr.rjust(size*2, '0')
```

pwndbg/commands/windbg.py

@@ -8,6 +8,8 @@ from __future__ import division
 from __future__ import print_function
 from __future__ import unicode_literals
 
+from builtins import str
+
 import argparse
 import codecs
 import math
@@ -172,9 +174,9 @@ def eX(size, address, data, hex=True):
     if address is None:
         return
 
-    for i,bytestr in enumerate(data):
+    for i, bytestr in enumerate(data):
         if hex:
-            bytestr = bytestr.rjust(size*2, '0')
+            bytestr = str(bytestr).rjust(size*2, '0')
             data    = codecs.decode(bytestr, 'hex')
         else:
             data    = bytestr

pwndbg/memory.py

@@ -100,7 +100,10 @@ def write(addr, data):
         addr(int): Address to write
         data(str,bytes,bytearray): Data to write
     """
-    gdb.selected_inferior().write_memory(addr, bytes(data, 'utf8'))
+    if isinstance(data, str):
+        data = bytes(data, 'utf8')
+
+    gdb.selected_inferior().write_memory(addr, data)
 
 
 def peek(address):