E3-1589: Fix truncated error logs

In EPICS base, the errorlog functionality is initialised with a default maximum error log size of 256. This means that error messages longer than that size show as `<>´, which means that we miss a number of important messages, in particular error messages due to missing symbols from shared libraries when they are loaded.

errlogInit unfortunately is a bit of a singleton; it can only be called a single time, and it is called when we load require the very first time.

require-ess/tools/iocsh_utils.py

@@ -8,6 +8,8 @@ import sys
 from tempfile import NamedTemporaryFile
 from pathlib import Path
 
+DEFAULT_ERRLOG_BUFFER_SIZE = 2048
+
 
 @atexit.register
 def graceful_shutdown() -> None:
@@ -30,6 +32,10 @@ class TemporaryStartupScript:
         self.set_variable("IOCSH_TOP", Path.cwd())
         self.set_variable("IOCSH_PS1", generate_prompt())
 
+        self.add_command(
+            f"errLogInit2 {DEFAULT_ERRLOG_BUFFER_SIZE} {DEFAULT_ERRLOG_BUFFER_SIZE}"
+        )
+
         # load require
         self.add_command(
             f"dlload {str(Path(os.environ['E3_REQUIRE_LIB']) / os.environ['EPICS_HOST_ARCH'] / 'librequire.so')}"