LineContinuationBear: Add ignore_with option

Add `ignore_with` option in LineContinuationBear to ignore
backslashes used in `with` statements.

Closes #2807

bears/general/LineContinuationBear.py

@@ -10,6 +10,7 @@ def run(self,
             filename,
             file,
             language,
+            ignore_with: bool = False,
             ):
         """
         It is a generic bear which will look for any lines which
@@ -27,6 +28,8 @@ def run(self,
             File that needs to be checked in the form of a list of strings.
         :param language:
             Language to be used for finding the line continuation tokens.
+        :param ignore_with:
+            Ignore line continuation operators in with statements.
         """
         try:
             lang = Language[language]
@@ -36,7 +39,7 @@ def run(self,
             return
 
         for line_number, line in enumerate(file):
-            if len(line) > 1:
+            if len(line) > 1 and not ignore_with:
                 if line[-2] in line_continuation:
                     yield Result.from_values(
                         origin=self,
@@ -46,4 +49,15 @@ def run(self,
                         column=len(line) - 1,
                         end_line=line_number + 1,
                         end_column=len(line),
-                        )
+                    )
+            elif len(line) > 1 and ignore_with:
+                if line[-2] in line_continuation and line[:5] != 'with ':
+                    yield Result.from_values(
+                        origin=self,
+                        message='Explicit line continuation is not allowed.',
+                        file=filename,
+                        line=line_number + 1,
+                        column=len(line) - 1,
+                        end_line=line_number + 1,
+                        end_column=len(line),
+                    )

tests/general/LineContinuationBearTest.py

@@ -34,6 +34,28 @@ def test_bad_file(self):
                                 line=1, column=9, end_line=1, end_column=10,
                                 file='default')],
             filename='default')
+        self.check_results(
+            self.uut, ["with open ('hey.txt') as \\",
+                       'heyfile'],
+            [Result.from_values('LineContinuationBear',
+                                'Explicit line continuation is not allowed.',
+                                line=1, column=26, end_line=1, end_column=27,
+                                file='default')],
+            filename='default')
+
+    def test_data_ignore_with(self):
+        self.section.append(Setting('language', 'Python'))
+        self.section.append(Setting('ignore_with', 'true'))
+        self.check_results(
+            self.uut, ['a = 1 + \\', '2'],
+            [Result.from_values('LineContinuationBear',
+                                'Explicit line continuation is not allowed.',
+                                line=1, column=9, end_line=1, end_column=10,
+                                file='default')],
+            filename='default')
+        self.check_validity(
+            self.uut, ["with open('hey.txt') as \\",
+                       'heyfile'])
 
     def test_lang_exception(self):
         self.section.append(Setting('language', 'BlaBlaBla'))