Simplify code to show GUI debug log

Fixes regression caused by Qt 5 behavior change that prevented the
debug log from being displayed in linux.

src/calibre/debug.py

@@ -41,9 +41,6 @@ Everything after the -- is passed to the script.
                       help=_('Run the GUI with a debug console, logging to the'
                       ' specified path. For internal use only, use the -g'
                       ' option to run the GUI in debug mode'))
-    parser.add_option('--show-gui-debug',  default=None,
-                      help=_('Display the specified log file. For internal use'
-                      ' only.'))
     parser.add_option('-w', '--viewer',  default=False, action='store_true',
                       help=_('Run the ebook viewer in debug mode'))
     parser.add_option('--paths', default=False, action='store_true',
@@ -220,18 +217,6 @@ def main(args=sys.argv):
         main(['calibre'])
     elif opts.gui_debug is not None:
         run_debug_gui(opts.gui_debug)
-    elif opts.show_gui_debug:
-        import time, re
-        time.sleep(1)
-        from calibre.gui2 import open_local_file
-        if iswindows:
-            with open(opts.show_gui_debug, 'r+b') as f:
-                raw = f.read()
-                raw = re.sub('(?<!\r)\n', '\r\n', raw)
-                f.seek(0)
-                f.truncate()
-                f.write(raw)
-        open_local_file(opts.show_gui_debug)
     elif opts.viewer:
         from calibre.gui2.viewer.main import main
         main(['ebook-viewer'] + args[1:])

src/calibre/gui2/main.py

@@ -1,7 +1,7 @@
 __license__   = 'GPL v3'
 __copyright__ = '2008, Kovid Goyal <kovid at kovidgoyal.net>'
 
-import sys, os, time, socket, traceback
+import sys, os, time, socket, traceback, re
 from functools import partial
 
 import apsw
@@ -349,14 +349,16 @@ def run_gui(opts, args, listener, app, gui_debug=None):
                 pass
     if getattr(runner.main, 'gui_debug', None) is not None:
         e = sys.executable if getattr(sys, 'frozen', False) else sys.argv[0]
-        import subprocess
-        creationflags = 0
+        debugfile = runner.main.gui_debug
+        from calibre.gui2 import open_local_file
         if iswindows:
-            import win32process
-            creationflags = win32process.CREATE_NO_WINDOW
-        subprocess.Popen([e, '--show-gui-debug', runner.main.gui_debug],
-            creationflags=creationflags, stdout=open(os.devnull, 'w'),
-            stderr=subprocess.PIPE, stdin=open(os.devnull, 'r'))
+            with open(debugfile, 'r+b') as f:
+                raw = f.read()
+                raw = re.sub(b'(?<!\r)\n', b'\r\n', raw)
+                f.seek(0)
+                f.truncate()
+                f.write(raw)
+        open_local_file(debugfile)
     return ret
 
 def cant_start(msg=_('If you are sure it is not running')+', ',