emake displays this message if an error occurs trying to write the contents of a file to disk.
In the process of writing the contents of a file created during the build to disk, emake was unable to open the file identified by path in the message. The OS error message provides the specific cause of the failure. Note that the path will be a location inside a temporary directory created by emake to store files created during the build between the time of creation and the time that the files are committed to their final location.
Because the error involves an external system in this case (the filesystem on the emake host), the list of possible causes for this error is virtually limitless: a corrupted filesystem; hardware failure; insufficient permissions; and so on. Refer to the specific OS error message to determine the cause of the failure.
The fix will depend on the specific cause of the error. For example, if the error states No space left on device, then you need to ensure that the device hosting the emake temporary directory has sufficient space to store the files created during the build. You may also be able to use the --emake-tmpdir command-line option to explicitly set the emake temporary directory location to another filesystem.