diff --git a/news/2905cccb-2fe8-4b0d-8734-303510a7e4ce.trivial.rst b/news/2905cccb-2fe8-4b0d-8734-303510a7e4ce.trivial.rst
new file mode 100644
index 000000000..e69de29bb
diff --git a/src/pip/_internal/vcs/bazaar.py b/src/pip/_internal/vcs/bazaar.py
index ee78b5d27..6af3e35ff 100644
--- a/src/pip/_internal/vcs/bazaar.py
+++ b/src/pip/_internal/vcs/bazaar.py
@@ -96,6 +96,7 @@ class Bazaar(VersionControl):
 
     @classmethod
     def get_revision(cls, location):
+        # type: (str) -> str
         revision = cls.run_command(
             ['revno'], cwd=location,
         )
diff --git a/src/pip/_internal/vcs/git.py b/src/pip/_internal/vcs/git.py
index e540e02dd..88a56d6ad 100644
--- a/src/pip/_internal/vcs/git.py
+++ b/src/pip/_internal/vcs/git.py
@@ -345,6 +345,7 @@ class Git(VersionControl):
 
     @classmethod
     def get_revision(cls, location, rev=None):
+        # type: (str, Optional[str]) -> str
         if rev is None:
             rev = 'HEAD'
         current_rev = cls.run_command(
diff --git a/src/pip/_internal/vcs/mercurial.py b/src/pip/_internal/vcs/mercurial.py
index e7988d1ac..98c288864 100644
--- a/src/pip/_internal/vcs/mercurial.py
+++ b/src/pip/_internal/vcs/mercurial.py
@@ -97,6 +97,7 @@ class Mercurial(VersionControl):
 
     @classmethod
     def get_revision(cls, location):
+        # type: (str) -> str
         """
         Return the repository-local changeset revision number, as an integer.
         """
diff --git a/src/pip/_internal/vcs/subversion.py b/src/pip/_internal/vcs/subversion.py
index b6b7010bf..0582ab0c7 100644
--- a/src/pip/_internal/vcs/subversion.py
+++ b/src/pip/_internal/vcs/subversion.py
@@ -49,6 +49,7 @@ class Subversion(VersionControl):
 
     @classmethod
     def get_revision(cls, location):
+        # type: (str) -> str
         """
         Return the maximum revision for all files under a given location
         """
@@ -73,7 +74,7 @@ class Subversion(VersionControl):
                 dirs[:] = []
                 continue    # not part of the same svn tree, skip it
             revision = max(revision, localrev)
-        return revision
+        return str(revision)
 
     @classmethod
     def get_netloc_and_auth(cls, netloc, scheme):