py3k strings byte us again, also simplify error handling and fix pyli…

…nt warnings

git-svn-id: https://xpra.org/svn/Xpra/trunk@21923 3bb7dfac-3a0b-4e04-842a-767bc560f471

src/xpra/platform/displayfd.py

@@ -1,15 +1,16 @@
 # This file is part of Xpra.
-# Copyright (C) 2017-2018 Antoine Martin <antoine@xpra.org>
+# Copyright (C) 2017-2019 Antoine Martin <antoine@xpra.org>
 # Xpra is released under the terms of the GNU GPL v2, or, at your option, any
 # later version. See the file COPYING for details.
 
 import os
 
-from xpra.os_util import monotonic_time
+from xpra.os_util import monotonic_time, strtobytes
 from xpra.util import envint
 
 DISPLAY_FD_TIMEOUT = envint("XPRA_DISPLAY_FD_TIMEOUT", 20)
 
+
 def eerrno(e):
     try:
         #python3:
@@ -21,19 +22,16 @@ def eerrno(e):
 def write_displayfd(w_pipe, display, timeout=10):
     import select   #@UnresolvedImport
     import errno
-    buf = b"%s\n" % display
+    buf = b"%s\n" % strtobytes(display)
     limit = monotonic_time()+timeout
     while buf and monotonic_time()<limit:
         try:
             timeout = max(0, limit-monotonic_time())
-            _, w, _ = select.select([], [w_pipe], [], timeout)
+            w = select.select([], [w_pipe], [], timeout)[1]
             if w_pipe in w:
                 count = os.write(w_pipe, buf)
                 buf = buf[count:]
-        except select.error as e:
-            if eerrno(e)!=errno.EINTR:
-                raise
-        except (OSError, IOError) as e:
+        except (select.error, OSError, IOError) as e:
             if eerrno(e)!=errno.EINTR:
                 raise
     return len(buf)==0
@@ -48,29 +46,26 @@ def read_displayfd(r_pipe, timeout=DISPLAY_FD_TIMEOUT, proc=None):
     while monotonic_time()<limit and len(buf)<8 and (proc is None or proc.poll() is None):
         try:
             timeout = max(0, limit-monotonic_time())
-            r, _, _ = select.select([r_pipe], [], [], timeout)
+            r = select.select([r_pipe], [], [], timeout)[0]
             if r_pipe in r:
                 buf += os.read(r_pipe, 8)
                 if buf and (buf[-1]==b'\n' or len(buf)>=8):
                     break
-        except select.error as e:
-            if eerrno(e)!=errno.EINTR:
-                raise
-        except (OSError, IOError) as e:
+        except (select.error, OSError, IOError) as e:
             if eerrno(e)!=errno.EINTR:
                 raise
     return buf
 
 def parse_displayfd(buf, err):
-    if len(buf) == 0:
+    if not buf:
         err("did not provide a display number using displayfd")
         return None
     if buf[-1] not in (b'\n', ord(b"\n")):
         err("output not terminated by newline: %s" % buf)
         return None
     try:
         n = int(buf[:-1])
-    except:
+    except ValueError:
         err("display number is not a valid number: %s" % buf[:-1])
     if n<0 or n>=2**16:
         err("provided an invalid display number: %s" % n)