Update for pydocstyle 2.0.0 compatibility

Fix #96

Adding the newer ignore_decorators argument. Thanks to @not-raspberry for the tip!

pylama/lint/pylama_pydocstyle.py

@@ -1,6 +1,13 @@
 """pydocstyle support."""
 
-from pydocstyle import PEP257Checker
+THIRD_ARG = True
+try:
+    #: Import for pydocstyle 2.0.0 and newer
+    from pydocstyle import ConventionChecker as PyDocChecker
+except ImportError:
+    #: Backward compatibility for pydocstyle prior to 2.0.0
+    from pydocstyle import PEP257Checker as PyDocChecker
+    THIRD_ARG = False
 
 from pylama.lint import Linter as Abstract
 
@@ -15,11 +22,12 @@ def run(path, code=None, **meta):
 
         :return list: List of errors.
         """
+        check_source_args = (code, path, None) if THIRD_ARG else (code, path)
         return [{
             'lnum': e.line,
             # Remove colon after error code ("D403: ..." => "D403 ...").
             'text': (e.message[0:4] + e.message[5:]
                      if e.message[4] == ':' else e.message),
             'type': 'D',
             'number': e.code
-        } for e in PEP257Checker().check_source(code, path)]
+        } for e in PyDocChecker().check_source(*check_source_args)]