Fix encoding issues related to Python 3 upgrade.

Python 3 str() is a unicode already, so can't be decoded.
subprocess.Popen needs to be in text mode (universal_newlines is the
oldest compatible kwarg for this) in order to do line-based buffering.
In general, all the filesystem encoding stuff we were doing is done by
Python itself now.

zenmap/zenmapCore/NmapCommand.py

@@ -87,39 +87,6 @@ paths_config = PathsConfig()
 log.debug(">>> Platform: %s" % sys.platform)
 
 
-def wrap_file_in_preferred_encoding(f):
-    """Wrap an open file to automatically decode its contents when reading from
-    the encoding given by locale.getpreferredencoding, or just return the file
-    if that doesn't work.
-
-    The nmap executable will write its output in whatever the system encoding
-    is. Nmap's output is usually all ASCII, but time zone it prints can be in a
-    different encoding. If it is not decoded correctly it will be displayed as
-    garbage characters. This function assists in reading the Nmap output. We
-    don't know for sure what the encoding used is, but we take a best guess and
-    decode the output into a proper unicode object so that the screen display
-    and XML writer interpret it correctly."""
-
-    try:
-        preferredencoding = locale.getpreferredencoding()
-    except locale.Error:
-        # This can happen if the LANG environment variable is set to something
-        # weird.
-        preferredencoding = None
-
-    if preferredencoding is not None:
-        try:
-            reader = codecs.getreader(preferredencoding)
-            return reader(f, "replace")
-        except LookupError:
-            # The lookup failed. This can happen if the preferred encoding is
-            # unknown ("X-MAC-KOREAN" has been observed). Ignore it and return
-            # the unwrapped file.
-            log.debug("Unknown encoding \"%s\"." % preferredencoding)
-
-    return f
-
-
 def escape_nmap_filename(filename):
     """Escape '%' characters so they are not interpreted as strftime format
     specifiers, which are not supported by Zenmap."""
@@ -235,8 +202,8 @@ class NmapCommand(object):
         # We don't need a file name for stdout output, just a handle. A
         # TemporaryFile is deleted as soon as it is closed, and in Unix is
         # unlinked immediately after creation so it's not even visible.
-        f = tempfile.TemporaryFile(mode="rb", prefix=APP_NAME + "-stdout-")
-        self.stdout_file = wrap_file_in_preferred_encoding(f)
+        f = tempfile.TemporaryFile(mode="r", prefix=APP_NAME + "-stdout-")
+        self.stdout_file = f
         if stderr is None:
             stderr = f
 
@@ -260,6 +227,7 @@ class NmapCommand(object):
                 startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
 
         self.command_process = subprocess.Popen(command_list, bufsize=1,
+                                     universal_newlines=True,
                                      stdin=subprocess.PIPE,
                                      stdout=f,
                                      stderr=stderr,