[BACKPORT 1.1.latest] Improved event log msg stringification (#7338)

* Add tests for logging jinja2.Undefined objects

[CT-2259](#7108) identifies
an issue wherein dbt-core 1.0-1.3 raise errors if a jinja2.Undefined
object is attempted to be logged. This generally happened in the form
of `{{ log(undefined_variable, info=True) }}`. This commit adding this
test exists for two reasons
1. Ensure we don't have a regression in this going forward
2. Exist as a commit to be used for backport fixes for dbt-core 1.0-1.3

* Add tests for checking `DBT_ENV_SECRET_`s don't break logging

[CT-1783](#6568) describes
a bug in dbt-core 1.0-1.3 wherein when a `DBT_ENV_SECRET_` all
`{{ log("logging stuff", info=True) }}` invocations break. This commit
adds a test for this for two reasons:
1. Ensure we don't regress to this behavior going forward
2. Act as a base commit for making the backport fixes to dbt-core 1.0-1.3

* Add changie info for changes

* Ensure `log()` calls from jinja ensure the msg is stringified

The simplest way to resolve [CT-2259](#7108)
and [CT-1783](#6568) in backports
to dbt-core < 1.4 is to ensure `msg` in `BaseContext.log()` is stringified.

.changes/unreleased/Fixes-20230331-095428.yaml

@@ -0,0 +1,6 @@
+kind: Fixes
+body: Improved failed event serialization handling and associated tests
+time: 2023-03-31T09:54:28.701963-07:00
+custom:
+  Author: QMalcolm
+  Issue: 7113 7108 6568

core/dbt/context/base.py

@@ -441,6 +441,10 @@ def log(msg: str, info: bool = False) -> str:
               {{ log("Running some_macro: " ~ arg1 ~ ", " ~ arg2) }}
             {% endmacro %}"
         """
+
+        if not isinstance(msg, str):
+            msg = str(msg)
+
         if info:
             fire_event(MacroEventInfo(msg=msg))
         else:

test/unit/test_base_context.py

@@ -0,0 +1,22 @@
+import os
+
+from dbt.context.base import BaseContext
+from jinja2.runtime import Undefined
+
+
+class TestBaseContext:
+    def test_log_jinja_undefined(self):
+        # regression test for CT-2259
+        try:
+            os.environ["DBT_ENV_SECRET_LOG_TEST"] = "cats_are_cool"
+            BaseContext.log(msg=Undefined(), info=True)
+        except Exception as e:
+            assert False, f"Logging an jinja2.Undefined object raises an exception: {e}"
+
+    def test_log_with_dbt_env_secret(self):
+        # regression test for CT-1783
+        try:
+            os.environ["DBT_ENV_SECRET_LOG_TEST"] = "cats_are_cool"
+            BaseContext.log({"fact1": "I like cats"}, info=True)
+        except Exception as e:
+            assert False, f"Logging while a `DBT_ENV_SECRET` was set raised an exception: {e}"