Fix minor error in exit_code_message; change to safe_dump

pyomo/common/config.py

@@ -1037,8 +1037,11 @@ class will still create ``c`` instances that only have the single
 
 
 def _dump(*args, **kwds):
+    # TODO: Change the default behavior to no longer be YAML.
+    # This was a legacy decision that may no longer be the best
+    # decision, given changes to technology over the years.
     try:
-        from yaml import dump
+        from yaml import safe_dump as dump
     except ImportError:
         # dump = lambda x,**y: str(x)
         # YAML uses lowercase True/False
@@ -1099,7 +1102,7 @@ def _value2string(prefix, value, obj):
         try:
             _data = value._data if value is obj else value
             if getattr(builtins, _data.__class__.__name__, None) is not None:
-                _str += _dump(_data, default_flow_style=True).rstrip()
+                _str += _dump(_data, default_flow_style=True, allow_unicode=True).rstrip()
                 if _str.endswith("..."):
                     _str = _str[:-3].rstrip()
             else:

pyomo/solver/results.py

@@ -326,6 +326,7 @@ def parse_sol_file(
             f"ERROR READING `sol` FILE. Expected `objno`; received {line}."
         )
     result.extra_info.solver_message = message.strip().replace('\n', '; ')
+    exit_code_message = ''
     if (exit_code[1] >= 0) and (exit_code[1] <= 99):
         result.solution_status = SolutionStatus.optimal
         result.termination_condition = TerminationCondition.convergenceCriteriaSatisfied
@@ -362,7 +363,8 @@ def parse_sol_file(
         result.termination_condition = TerminationCondition.error
 
     if result.extra_info.solver_message:
-        result.extra_info.solver_message += '; ' + exit_code_message
+        if exit_code_message:
+            result.extra_info.solver_message += '; ' + exit_code_message
     else:
         result.extra_info.solver_message = exit_code_message