From 1b8c325d832b23f39431cc34273e5dbb09af889f Mon Sep 17 00:00:00 2001
From: Manuel Barkhau <mbarkhau@gmail.com>
Date: Mon, 8 Jul 2019 15:39:04 +0000
Subject: [PATCH] Don't fail when ENABLE_BACKTRACE=1 but backtrace is not
 available.

---
 src/pycalver/cli.py | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/pycalver/cli.py b/src/pycalver/cli.py
index a804b4a..6cb034e 100755
--- a/src/pycalver/cli.py
+++ b/src/pycalver/cli.py
@@ -28,9 +28,12 @@ _VERBOSE = 0
 # To enable pretty tracebacks:
 #   echo "export ENABLE_BACKTRACE=1;" >> ~/.bashrc
 if os.environ.get('ENABLE_BACKTRACE') == '1':
-    import backtrace
+    try
+        import backtrace
 
-    backtrace.hook(align=True, strip_path=True, enable_on_envvar_only=True)
+        backtrace.hook(align=True, strip_path=True, enable_on_envvar_only=True)
+    except ImportError:
+        pass
 
 
 click.disable_unicode_literals_warning = True