def errch(marker, string):
marker = stypes.stringToCharP(marker)<EOL>string = stypes.stringToCharP(string)<EOL>libspice.errch_c(marker, string)<EOL>
Substitute a character string for the first occurrence of
a marker in the current long error message.

http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/errch_c.html

:param marker: A substring of the error message to be replaced.
:type marker: str
:param string: The character string to substitute for marker.
:type string: str