From 79d2e486a34911ada6d81701f14dd3c4b9790afd Mon Sep 17 00:00:00 2001
From: Mark Bailey <msb@eastface.co.uk>
Date: Mon, 23 Dec 2019 22:46:03 +0000
Subject: [PATCH] Fix TypeError in parser wrapper logic

In attempting to pass-through the string representation of an exception
we are wrapping, we made the erroneous assumption that `args[0]` would
always be a string (or something that can concatenate cleanly with a
string). This turns out not to be the case with `IllegalMonthError`,
where it is an integer, so to avoid raising an erroneous `TypeError`, we
first convert the wrapped exception to a string.

See GH issue #981.
---
 changelog.d/987.bugfix.rst   | 4 ++++
 dateutil/parser/_parser.py   | 2 +-
 dateutil/test/test_parser.py | 4 ++++
 3 files changed, 9 insertions(+), 1 deletion(-)
 create mode 100644 changelog.d/987.bugfix.rst

diff --git a/changelog.d/987.bugfix.rst b/changelog.d/987.bugfix.rst
new file mode 100644
index 000000000..8bc3cdd57
--- /dev/null
+++ b/changelog.d/987.bugfix.rst
@@ -0,0 +1,4 @@
+Fixed a bug in the parser where non-``ValueError`` exceptions would be raised
+during exception handling; this would happen, for example, if an
+``IllegalMonthError`` was raised in ``dateutil`` code. Fixed by Mark Bailey.
+(gh issue #981, pr #987).
diff --git a/dateutil/parser/_parser.py b/dateutil/parser/_parser.py
index 458aa6a32..7fcfa5457 100644
--- a/dateutil/parser/_parser.py
+++ b/dateutil/parser/_parser.py
@@ -654,7 +654,7 @@ def parse(self, timestr, default=None,
         try:
             ret = self._build_naive(res, default)
         except ValueError as e:
-            six.raise_from(ParserError(e.args[0] + ": %s", timestr), e)
+            six.raise_from(ParserError(str(e) + ": %s", timestr), e)
 
         if not ignoretz:
             ret = self._build_tzaware(ret, res, tzinfos)
diff --git a/dateutil/test/test_parser.py b/dateutil/test/test_parser.py
index 726156c8d..605705e4c 100644
--- a/dateutil/test/test_parser.py
+++ b/dateutil/test/test_parser.py
@@ -743,6 +743,10 @@ def test_out_of_bound_day(self):
         with pytest.raises(ParserError):
             parse("Feb 30, 2007")
 
+    def test_illegal_month_error(self):
+        with pytest.raises(ParserError):
+            parse("0-100")
+
     def test_day_sanity(self, fuzzy):
         dstr = "2014-15-25"
         with pytest.raises(ParserError):