Format of ILIAS Exceptions in Checkout App

[SebastianOpriel]

If the REST plugin causes an ILIAS error, a letter separated HTML document is shown as response in the Checkout app (tested with ILIAS 5.2.9 and 5.3.6)

Result
{
  0: "<",
  1: "!",
  2: "D",
  3: "O",
  4: "C",
  5: "T",
  6: "Y",
  7: "P",
  8: "E",
  9: " ",
  10: "h",
  11: "t",
  12: "m",
  13: "l",
  14: ">",
  15: "\n",
  16: "<",
  17: "h",
  18: "t",
  19: "m",
  20: "l",
  21: " ",
  22: "l",
  23: "a",
  24: "n",
  25: "g",
  26: "=",
  27: """,
  28: """,
  29: " ",
...