Use the real constants module.

This is progressing refactor of the calibre code to make it more
readable, and transform it to something more coherent.

In this patch, there are changes regarding imports for some modules,
instead of polluting namespace of each module with some other modules
symbols, which often were imported from other modules. Yuck.

ebook_converter/startup.py

@@ -10,7 +10,7 @@ import builtins
 import locale
 import sys
 
-from ebook_converter import constants
+from ebook_converter import constants_old
 
 # For backwards compat with some third party plugins
 builtins.__dict__['dynamic_property'] = lambda func: func(None)
@@ -41,8 +41,8 @@ if not _run_once:
 
     #
     # Platform specific modules
-    if constants.iswindows:
-        winutil, winutilerror = constants.plugins['winutil']
+    if constants_old.iswindows:
+        winutil, winutilerror = constants_old.plugins['winutil']
         if not winutil:
             raise RuntimeError('Failed to load the winutil plugin: %s'%winutilerror)
         if len(sys.argv) > 1 and not isinstance(sys.argv[1], str):
@@ -57,8 +57,8 @@ if not _run_once:
 
     #
     # Convert command line arguments to unicode
-    enc = constants.preferred_encoding
-    if constants.isosx:
+    enc = constants_old.preferred_encoding
+    if constants_old.isosx:
         enc = 'utf-8'
     for i in range(1, len(sys.argv)):
         if not isinstance(sys.argv[i], str):
@@ -66,7 +66,7 @@ if not _run_once:
 
     #
     # Ensure that the max number of open files is at least 1024
-    if constants.iswindows:
+    if constants_old.iswindows:
         # See https://msdn.microsoft.com/en-us/library/6e3b887c.aspx
         if hasattr(winutil, 'setmaxstdio'):
             winutil.setmaxstdio(max(1024, winutil.getmaxstdio()))
@@ -77,7 +77,7 @@ if not _run_once:
             try:
                 resource.setrlimit(resource.RLIMIT_NOFILE, (min(1024, hard), hard))
             except Exception:
-                if constants.DEBUG:
+                if constants_old.DEBUG:
                     import traceback
                     traceback.print_exc()
 
@@ -122,7 +122,7 @@ if not _run_once:
         bound_signal.connect(slot, **kw)
     builtins.__dict__['connect_lambda'] = connect_lambda
 
-    if constants.islinux or constants.isosx or constants.isfreebsd:
+    if constants_old.islinux or constants_old.isosx or constants_old.isfreebsd:
         # Name all threads at the OS level created using the threading module, see
         # http://bugs.python.org/issue15500
         import threading
@@ -140,7 +140,7 @@ if not _run_once:
                 if name:
                     if isinstance(name, str):
                         name = name.encode('ascii', 'replace').decode('ascii')
-                    constants.plugins['speedup'][0].set_thread_name(name[:15])
+                    constants_old.plugins['speedup'][0].set_thread_name(name[:15])
             except Exception:
                 pass  # Don't care about failure to set name
         threading.Thread.start = new_start
@@ -152,7 +152,7 @@ def test_lopen():
     n = 'f\xe4llen'
     print('testing open()')
 
-    if constants.iswindows:
+    if constants_old.iswindows:
         import msvcrt, win32api
 
         def assert_not_inheritable(f):