BootCamp partition error even though my drive is one partition I am attempting to install Windows 8.1 on my machine (a mid 2014 MacBook Pro running El Capitan) and I keep running into a BootCamp error in the first step that says 


  The startup disk must be formatted as a single Mac OS Extended (Journaled) volume or already partitioned by Boot Camp Assistant for installing Windows.


However, the startup disk is partitioned as a single HFS+ partition as verified by the output below: 

$diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.3 GB   disk0
   1:                  Apple_HFS MAC HDD                 499.9 GB   disk0s1


Why does Boot Camp think my disk is not partitioned correctly?

I've read several posts about this error message, but all describe how to repartition the drive instead of why a correctly partitioned drive may cause this error.
I was able to install Windows after doing two things. I'm not positive which one did the trick as I did them both in between an attempt to run bootcamp. These are the things I did in order:


Install reFind... doing this added the missing EFI partition that was mentioned I was missing in the comments for this question.
Use the reFind partition editor to fix the Master Boot Record (MBR) table for my HDD. This partition editor can be found on the reFit menu (launched by choosing the reFit option on the reFind menu)


After this, I launched mac, started boot camp, and the 'status: partitioning disk' message/bar restarted and then it was able to finish partitioning and I have since installed Windows successfully. Any hints on why this finally worked would be much appreciated!

Also, something to note is that after I installed reFind, my partition table (output to diskutil list) was: 

/dev/disk0 (internal, physical):
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      GUID_partition_scheme                        *500.3 GB   disk0
1:                        EFI EFI                     209.7 MB   disk0s1
2:                  Apple_HFS MAC HDD                 500.1 GB   disk0s2