Use split_markdown_front_matter helper in istio

also, sort imports

Signed-off-by: Hritik Vijay <hritikxx8@gmail.com>

Author: Hritik14

vulnerabilities/helpers.py

@@ -170,7 +170,7 @@ def __lt__(self, other):
 def split_markdown_front_matter(text: str) -> Tuple[str, str]:
     r"""
     Split text into markdown front matter and the markdown body
-    Returns ("", text) for text with non existing front matter
+    Return ("", text) for text with non existing front matter
 
     >>> text='''---
     ... title: DUMMY-SECURITY-2019-001

vulnerabilities/importers/istio.py

@@ -22,14 +22,16 @@
 
 import asyncio
 import re
-from typing import List, Set
-import yaml
+from typing import Set
 
+import yaml
+from packageurl import PackageURL
 from univers.version_specifier import VersionSpecifier
 from univers.versions import SemverVersion
-from packageurl import PackageURL
 
-from vulnerabilities.data_source import Advisory, GitDataSource, Reference
+from vulnerabilities.data_source import Advisory
+from vulnerabilities.data_source import GitDataSource
+from vulnerabilities.helpers import split_markdown_front_matter
 from vulnerabilities.package_managers import GitHubTagsAPI
 from vulnerabilities.helpers import nearest_patched_package
 
@@ -78,45 +80,6 @@ def get_pkg_versions_from_ranges(self, version_range_list):
         safe_pkg_versions = set(all_version) - set(vuln_pkg_versions)
         return safe_pkg_versions, vuln_pkg_versions
 
-    def get_data_from_yaml_lines(self, yaml_lines):
-        """Return a mapping of data from a iterable of yaml_lines
-        for example :
-            ['title: ISTIO-SECURITY-2019-001',
-            'description: Incorrect access control.','cves: [CVE-2019-12243]']
-
-            would give {'title':'ISTIO-SECURITY-2019-001',
-            'description': 'Incorrect access control.',
-            'cves': '[CVE-2019-12243]'}
-        """
-
-        return yaml.safe_load("\n".join(yaml_lines))
-
-    def get_yaml_lines(self, lines):
-        """The istio advisory file contains lines similar to yaml format .
-        This function extracts those lines and return an iterable of lines
-
-        for example :
-            lines =
-            ---
-            title: ISTIO-SECURITY-2019-001
-            description: Incorrect access control.
-            cves: [CVE-2019-12243]
-            ---
-
-        get_yaml_lines(lines) would return
-        ['title: ISTIO-SECURITY-2019-001','description: Incorrect access control.'
-        ,'cves: [CVE-2019-12243]']
-        """
-
-        for index, line in enumerate(lines):
-            line = line.strip()
-            if line.startswith("---") and index == 0:
-                continue
-            elif line.endswith("---"):
-                break
-            else:
-                yield line
-
     def process_file(self, path):
 
         advisories = []
@@ -199,10 +162,10 @@ def process_file(self, path):
         return advisories
 
     def get_data_from_md(self, path):
-        """Return a mapping of vulnerability data from istio . The data is
-        in the form of yaml_lines inside a .md file.
+        """Return a mapping of vulnerability data from istio. The data is
+        in the form of yaml objects found inside front matter of the .md file.
         """
 
         with open(path) as f:
-            yaml_lines = self.get_yaml_lines(f)
-            return self.get_data_from_yaml_lines(yaml_lines)
+            yaml_lines, _ = split_markdown_front_matter(f.read())
+            return yaml.safe_load(yaml_lines)