encode tparm output as latin1

as explained in the comments above the decode().encode() wrapper,
certain terminal kinds, such as 'avatar' or 'kermit' emit 8-bit bytes
that are not legal utf-8 tender. this issue is resolved by encoding
these values as latin1, which leaves their values unmolested. This is
exaplified by a gist: https://gist.github.com/jquast/5649654

If you don't believe me, try kind='kermit' or kind='avatar', along with
t.cup(n, n). Unfortunately, the state of the test cases in the master
branch (issue #33) does not allow to add a test case in this branch
until that one is pulled to master.

Hell, I'll go ahead and make a third (and final) pull request for that one,

2 files changed, 11 insertions, 4 deletions

diff --git a/blessings/__init__.py b/blessings/__init__.py
index b135e01..d968bb5 100644
--- a/blessings/__init__.py
+++ b/blessings/__init__.py
@@ -367,7 +367,7 @@ class Terminal(object):
             # We can encode escape sequences as UTF-8 because they never
             # contain chars > 127, and UTF-8 never changes anything within that
             # range..
-            return code.decode('utf-8')
+            return code.decode('latin1')
         return u''
 
     def _resolve_color(self, color):
@@ -436,7 +436,14 @@ class ParametrizingString(unicode):
             # Re-encode the cap, because tparm() takes a bytestring in Python
             # 3. However, appear to be a plain Unicode string otherwise so
             # concats work.
-            parametrized = tparm(self.encode('utf-8'), *args).decode('utf-8')
+            # We use *latin1* encoding so that bytes emitted by tparam are
+            # encoded to their native value: some terminal kinds, such as
+            # 'avatar' or 'kermit', emit 8-bit bytes in range 0x7f to 0xff.
+            # latin1 leaves these values unmodified in their conversion to
+            # unicode byte values. The terminal emulator will 'catch' and
+            # handle these values, even if emitting utf8 encoded text, where
+            # these bytes would otherwise be illegal utf8 start bytes.
+            parametrized = tparm(self.encode('latin1'), *args).decode('latin1')
             return (parametrized if self._normal is None else
                     FormattingString(parametrized, self._normal))
         except curses.error:
diff --git a/blessings/tests.py b/blessings/tests.py
index 7dda746..15141dc 100644
--- a/blessings/tests.py
+++ b/blessings/tests.py
@@ -28,12 +28,12 @@ TestTerminal = partial(Terminal, kind='xterm-256color')
 
 def unicode_cap(cap):
     """Return the result of ``tigetstr`` except as Unicode."""
-    return tigetstr(cap).decode('utf-8')
+    return tigetstr(cap).decode('latin1')
 
 
 def unicode_parm(cap, *parms):
     """Return the result of ``tparm(tigetstr())`` except as Unicode."""
-    return tparm(tigetstr(cap), *parms).decode('utf-8')
+    return tparm(tigetstr(cap), *parms).decode('latin1')
 
 
 def test_capability():