Check for errors before writing a file to the archive.

def _writecheck(self, zinfo):
        """Check for errors before writing a file to the archive."""
        if zinfo.filename in self.NameToInfo:
            if self.debug:      # Warning for duplicate names
                print "Duplicate name:", zinfo.filename
        if self.mode not in ("w", "a"):
            raise RuntimeError, 'write() requires mode "w" or "a"'
        if not self.fp:
            raise RuntimeError, \
                  "Attempt to write ZIP archive that was already closed"
        if zinfo.compress_type == ZIP_DEFLATED and not zlib:
            raise RuntimeError, \
                  "Compression requires the (missing) zlib module"
        if zinfo.compress_type not in (ZIP_STORED, ZIP_DEFLATED):
            raise RuntimeError, \
                  "That compression method is not supported"
        if zinfo.file_size > ZIP64_LIMIT:
            if not self._allowZip64:
                raise LargeZipFile("Filesize would require ZIP64 extensions")
        if zinfo.header_offset > ZIP64_LIMIT:
            if not self._allowZip64:
                raise LargeZipFile("Zipfile size would require ZIP64 extensions")