Extra space at end of variable inserted in a json payload POST to a Flask webhook.

I have alerts setup to trigger on syslogs and I do not know how to remove the extra space at the end of a variable I have inserted into the body of my JSON POST.  It's from the variable (I believe), so I don't know how to parse it python or what I am doing wrong. 

Here is the body:

{
    "sylog": "${N=OLM.AlertingMacros;M=OLMAlertMessage.EventMessage}"
}

And here is the actual json I pulled from a packet capture:

{
    "sylog": "2028218 LC/0/2/CPU0:Oct 11 18:35:59.915 EDT: pfm_node_lc[294]: %PLATFORM-CFP-2-LANE_2_HIGH_BIAS_ALARM  :Set|envmon_lc[163927]|0x102b014|HundredGigE0/2/1/0
"
}

If I put that in a json validator, hit a backspace between the last " and the end of the string, it clears the json errors.

Any ideas?