shallow-backup crashes if repo can't be created

Fixes #308

shallow_backup/git_wrapper.py

@@ -2,6 +2,7 @@
 from pathlib import Path
 import sys
 import git
+from git import GitCommandError
 from shutil import move
 from .printing import *
 from .config import get_config
@@ -71,8 +72,12 @@ def safe_git_init(dir_path) -> (git.Repo, bool):
     """
     if not os.path.isdir(os.path.join(dir_path, ".git")):
         print_yellow_bold("Initializing new git repo...")
-        repo = git.Repo.init(dir_path)
-        return repo, True
+        try:
+            repo = git.Repo.init(dir_path)
+            return repo, True
+        except GitCommandError:
+            print_red_bold("ERROR: We ran into some trouble creating the git repo. Double check that you have write permissions.")
+            sys.exit(1)
     else:
         print_yellow_bold("Detected git repo.")
         repo = git.Repo(dir_path)