For stdpy.file wrapper, handle mode more consistently with Python.

For Python 2, ignore unknown characters in the mode rather than silently failing to open.
For Python 3, fail if unknown characters appear.

direct/src/stdpy/file.py

@@ -11,6 +11,7 @@ __all__ = [
     ]
 
 from panda3d import core
+import sys
 import types
 
 _vfs = core.VirtualFileSystem.getGlobalPtr()
@@ -65,12 +66,27 @@ class file:
             self.filename = filename
             self.name = filename.toOsSpecific()
 
+            if sys.version_info >= (3, 0):
+                # Python 3 is much stricter than Python 2, which lets
+                # unknown flags fall through.
+                for ch in mode:
+                    if not ch in 'rwxabt+U':
+                        raise IOError("invalid mode: " + mode)
+
             binary = False
+            if 'b' in mode and 't' in mode:
+                raise IOError("can't have text and binary mode at once")
+            
             if 'b' in mode:
                 # Strip 'b'.  This means a binary file.
                 i = mode.index('b')
                 mode = mode[:i] + mode[i + 1:]
                 binary = True
+            elif 't' in mode:
+                # Strip 't'.  This means a text file (redundant, yes).
+                i = mode.index('t')
+                mode = mode[:i] + mode[i + 1:]
+                binary = False
 
             if 'U' in mode:
                 # Strip 'U'.  We don't use it; universal-newline support
@@ -83,61 +99,69 @@ class file:
                 mode = 'r'
 
             # Per Python docs, we insist this is true.
-            assert mode[0] in 'rwa'
+            modeType = mode[0]
+            assert modeType in 'rwa'
 
             if binary:
                 filename.setBinary()
             else:
                 filename.setText()
-
-            # Actually open the streams.
-            if mode == 'w':
-                self.__stream = _vfs.openWriteFile(filename, autoUnwrap, True)
+            
+            # Actually open the streams, taking care to 
+            # ignore unknown chars in the mode string.
+            # We already asserted that it starts with a mode
+            # char above, so locate the '+'  
+            if modeType == 'w' and '+' in mode:
+                self.__stream = _vfs.openReadWriteFile(filename, True)
                 if not self.__stream:
                     message = 'Could not open %s for writing' % (filename)
-                    raise IOError, message
+                    raise IOError(message)
+                readMode = True
                 writeMode = True
 
-            elif mode == 'a':
-                self.__stream = _vfs.openAppendFile(filename)
+            elif modeType == 'a' and '+' in mode:
+                self.__stream = _vfs.openReadAppendFile(filename)
                 if not self.__stream:
                     message = 'Could not open %s for writing' % (filename)
-                    raise IOError, message
+                    raise IOError(message)
+                readMode = True
                 writeMode = True
 
-            elif mode == 'w+':
-                self.__stream = _vfs.openReadWriteFile(filename, True)
+            elif modeType == 'r' and '+' in mode:
+                self.__stream = _vfs.openReadWriteFile(filename, False)
                 if not self.__stream:
                     message = 'Could not open %s for writing' % (filename)
-                    raise IOError, message
+                    raise IOError(message)
                 readMode = True
                 writeMode = True
-
-            elif mode == 'a+':
-                self.__stream = _vfs.openReadAppendFile(filename)
+                
+            elif modeType == 'w':
+                self.__stream = _vfs.openWriteFile(filename, autoUnwrap, True)
                 if not self.__stream:
                     message = 'Could not open %s for writing' % (filename)
-                    raise IOError, message
-                readMode = True
+                    raise IOError(message)
                 writeMode = True
 
-            elif mode == 'r+':
-                self.__stream = _vfs.openReadWriteFile(filename, False)
+            elif modeType == 'a':
+                self.__stream = _vfs.openAppendFile(filename)
                 if not self.__stream:
                     message = 'Could not open %s for writing' % (filename)
-                    raise IOError, message
-                readMode = True
+                    raise IOError(message)
                 writeMode = True
 
-            elif mode == 'r':
+            elif modeType == 'r':
                 self.__stream = _vfs.openReadFile(filename, autoUnwrap)
                 if not self.__stream:
                     if not _vfs.exists(filename):
                         message = 'No such file: %s' % (filename)
                     else:
                         message = 'Could not open %s for reading' % (filename)
-                    raise IOError, message
+                    raise IOError(message)
                 readMode = True
+                
+            else:
+                # should not get here unless there's a bug above
+                raise IOError("Unhandled mode flags: " + mode)
 
             self.__needsVfsClose = True