title: Appending to file fails in Azure storage account
body: <p>I am attempting to write log files for operations in an Azure Databrick.  The log files are written to a file in a Azure storage account.  I am using Python to do this.  As a test, I set up 2 write operations.  The first one writes to a microsecond-timestamped log file, the name essentially being guaranteed to be unique.  The second attempts to write to one called &quot;log&quot;, in the same directory, and should simply append the new log lines to the ones already in the file.  Here's the very simple code:</p>
  <pre><code>log_file = log_dir + '/' + 'log_' + str(log_ts)
  with open(log_file, 'a') as l:
    l.write('\n'.join(log_lines_list))
    
  log_file = log_dir + '/' + 'log'
  with open(log_file, 'a') as l:
    l.write('\n'.join(log_lines_list))
  </code></pre>
  <p>There's not really much I see that can go wrong there.  The first file is created and written properly.  The second is unaltered, even the timestamp remaining unaltered; that is, the first run (file creation) of the code works, but subsequent runs (file appends) fail with the following error:</p>
  <pre><code>OSError: [Errno 95] Operation not supported
  ---------------------------------------------------------------------------
  OSError                                   Traceback (most recent call last)
  OSError: [Errno 95] Operation not supported
  
  During handling of the above exception, another exception occurred:
  
  OSError                                   Traceback (most recent call last)
  &lt;command-2639275445480394&gt; in &lt;module&gt;
       45 log_file = log_dir + '/' + 'log'
       46 with open(log_file, 'a') as l:
  ---&gt; 47   l.write('\n'.join(log_lines_list))
  
  OSError: [Errno 95] Operation not supported
  </code></pre>
  <p>My research has basically concluded that append operations are not valid in this type of storage.  Is that right?  That seems odd to me, but I am rather new to this.  I suppose I could read the file into a list, append the new lines to the list, rename the file, and write the joined list to a file of the previous name, and delete the renamed file once write is confirmed, but that really seems excessive.  Am I missing something here?</p>