Unable to access issue attachment if the filename contains non-ASCII character

Summary

Bitbucket raises "Something went wrong" error when user tries to access attachment on issue tracker if the file named in non-ASCII.

How to Replicate

• Create an arbitrary file named in non-ASCII characters such as by echo "Hello" >> "日本語.txt"
• Create a repository
• Enable issue tracker
• Go to Create issue > Select files > Choose the file created at 1st step > Select Create issue
• Access the file's link
• Confirm Bitbucket raises "Something went wrong" error

Investigation Done

Bitbucket Cloud complains the error below:

UnicodeDecodeError: 'ascii' codec can't decode byte 0xe6 in position 198: ordinal not in range(128)

Verified at https://bitbucket.org/i05/issue_tracker_15563/issues/1/jpns-18533 (private).