Prospectus excerpt:  We are offering 4,600,000 of our 8.875% Series E Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units, liquidation preference $25.00 per unit (or the Series E Preferred Units). Distributions on the Series E Preferred Units are cumulative from the date of original issue and will be payable quarterly in arrears on the 15th day of February, May, August and November of each year, when, as and if declared by the board of directors of our general partner. The initial distribution on the Series E Preferred Units offered hereby will be payable on May 15, 2018 in an amount equal to $0.69028 per unit. Distributions will be payable out of amounts legally available for distributions (i) from and including the original issue date to, but excluding February 15, 2025 at a fixed rate equal to 8.875% per annum of the stated liquidation preference and (ii) from and including February 15, 2025, at a floating rate equal to three-month LIBOR plus a spread of 640.7 basis points.