Fix more errors caught by mypy 0.501.

Another set of relatively easy to review changes.

tools/documentation_crawler/documentation_crawler/spiders/check_documentation.py

@@ -23,5 +23,5 @@ def get_start_url():
 class DocumentationSpider(BaseDocumentationSpider):
     name = "documentation_crawler"
     deny_domains = ['localhost:9991']
-    deny = '\_sources\/.*\.txt'
+    deny = ['\_sources\/.*\.txt']
     start_urls = get_start_url()

tools/documentation_crawler/documentation_crawler/spiders/common/spiders.py

@@ -18,7 +18,7 @@ class BaseDocumentationSpider(scrapy.Spider):
     # Exclude domain address.
     deny_domains = []  # type: List[str]
     start_urls = []  # type: List[str]
-    deny = ()  # type: Tuple
+    deny = []  # type: List[str]
     file_extensions = ['.' + ext for ext in IGNORED_EXTENSIONS]  # type: List[str]
     tags = ('a', 'area', 'img')
     attrs = ('href', 'src')