Partially revert https://gitlab.com/m2crypto/m2crypto/commit/738cd0bf3dc2ee619f598290d5bf4c2190987f16:

 * Fix BIO.File ... return type of BIO.readline() and close properly.
   That is, flush BIO.File() before closing and close also underlying
   system file.

For Python 2 this results in:

python2 -c "import M2Crypto; M2Crypto.BIO.openfile('/etc/ssl/cert.pem')"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/local/lib/python2.7/site-packages/M2Crypto/BIO.py", line 284, in openfile
    return File(f)
  File "/usr/local/lib/python2.7/site-packages/M2Crypto/BIO.py", line 239, in __init__
    pyfile.flush()
IOError: [Errno 9] Bad file descriptor

https://gitlab.com/m2crypto/m2crypto/issues/211

Index: src/M2Crypto/BIO.py
--- src/M2Crypto/BIO.py.orig
+++ src/M2Crypto/BIO.py
@@ -235,8 +235,9 @@ class File(BIO):
         #
         #  https://docs.python.org/3.3/c-api/file.html
         #
-        pyfile.flush()
-        self.fname = pyfile.name
+        if six.PY3:
+            pyfile.flush()
+            self.fname = pyfile.name
         self.pyfile = pyfile
         # Be wary of https://github.com/openssl/openssl/pull/1925
         # BIO_new_fd is NEVER to be used before OpenSSL 1.1.1
@@ -246,7 +247,8 @@ class File(BIO):
             self.bio = m2.bio_new_pyfile(pyfile, m2.bio_noclose)
 
         self.close_pyfile = close_pyfile
-        self.closed = False
+        if six.PY3:
+            self.closed = False
 
     def flush(self):
         # type: () -> None
@@ -255,8 +257,9 @@ class File(BIO):
 
     def close(self):
         # type: () -> None
-        self.flush()
-        super(File, self).close()
+        if six.PY3:
+            self.flush()
+            super(File, self).close()
         if self.close_pyfile:
             self.pyfile.close()