Issue #7865: The close() method of :mod:io objects should not swallow

exceptions raised by the implicit flush().  Also ensure that calling
close() several times is supported.  Patch by Pascal Chambon.

Lib/_pyio.py

@@ -327,6 +327,7 @@ class IOBase:
 
         This is not implemented for read-only and non-blocking streams.
         """
+        self._checkClosed()
         # XXX Should this return the number of bytes written???
 
     __closed = False
@@ -337,10 +338,7 @@ class IOBase:
         This method has no effect if the file is already closed.
         """
         if not self.__closed:
-            try:
-                self.flush()
-            except IOError:
-                pass  # If flush() fails, just give up
+            self.flush()
             self.__closed = True
 
     def __del__(self):
@@ -709,14 +707,13 @@ class _BufferedIOMixin(BufferedIOBase):
     ### Flush and close ###
 
     def flush(self):
+        if self.closed:
+            raise ValueError("flush of closed file")
         self.raw.flush()
 
     def close(self):
-        if not self.closed and self.raw is not None:
-            try:
-                self.flush()
-            except IOError:
-                pass  # If flush() fails, just give up
+        if self.raw is not None and not self.closed:
+            self.flush()
             self.raw.close()
 
     def detach(self):
@@ -1531,11 +1528,8 @@ class TextIOWrapper(TextIOBase):
         self._telling = self._seekable
 
     def close(self):
-        if self.buffer is not None:
-            try:
-                self.flush()
-            except IOError:
-                pass  # If flush() fails, just give up
+        if self.buffer is not None and not self.closed:
+            self.flush()
             self.buffer.close()
 
     @property