From 5b5540581396b07404018664f0954f2d13377753 Mon Sep 17 00:00:00 2001
From: Leonard Richardson <leonardr@segfault.org>
Date: Mon, 24 Dec 2018 10:17:54 -0500
Subject: Issue a warning and raise a more useful exception if someone tries to
 call Tag.select() without SoupSieve installed.

---
 NEWS.txt       | 14 ++++++++++++++
 bs4/element.py | 15 +++++++++++++--
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/NEWS.txt b/NEWS.txt
index 6e44504..4f5278a 100644
--- a/NEWS.txt
+++ b/NEWS.txt
@@ -1,5 +1,19 @@
 = 4.7.0 (Unreleased)
 
+* Beautiful Soup's CSS Selector implementation has been replaced by a
+  dependency on Isaac Muse's SoupSieve project (the soupsieve package
+  on PyPI). The good news is that SoupSieve has a much more robust and
+  complete implementation of CSS selectors, resolving a large number
+  of longstanding issues. The bad news is that from this point onward,
+  SoupSieve must be installed if you want to use the select() method.
+
+  You don't have to change anything lf you installed Beautiful Soup
+  through pip (SoupSieve will be automatically installed when you
+  upgrade Beautiful Soup) or if you don't use CSS selectors from
+  within Beautiful Soup.
+
+  SoupSieve documentation: https://facelessuser.github.io/soupsieve/
+
 * Fix a number of problems with the tree builder that caused
   trees that were superficially okay, but which fell apart when bits
   were extracted. Patch by Isaac Muse. [bug=1782928]
diff --git a/bs4/element.py b/bs4/element.py
index 7734f80..97403c9 100644
--- a/bs4/element.py
+++ b/bs4/element.py
@@ -9,7 +9,14 @@ except ImportError , e:
 import re
 import sys
 import warnings
-import soupsieve
+try:
+    import soupsieve
+except ImportError, e:
+    soupsieve = None
+    warnings.warn(
+        'The soupsieve package is not installed. CSS selectors cannot be used.'
+    )
+
 from bs4.dammit import EntitySubstitution
 
 DEFAULT_OUTPUT_ENCODING = "utf-8"
@@ -1347,7 +1354,11 @@ class Tag(PageElement):
         
         if limit is None:
             limit = 0
-
+        if soupsieve is None:
+            raise NotImplementedError(
+                "Cannot execute CSS selectors because the soupsieve package is not installed."
+            )
+            
         return soupsieve.select(selector, self, namespaces, limit, **kwargs)
 
     # Old names for backwards compatibility
-- 
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