main: install pipgrip in livecheck mode if needed

main.rb

@@ -98,9 +98,12 @@ def read_brew(*args)
     version = Version.parse tag
     url = stable.url.gsub stable.version, version
 
+    # Check if formula is originating from PyPi
     pypi_url = PyPI.update_pypi_url(stable.url, version)
     if pypi_url
+      # Substitute url
       url = pypi_url
+      # Install pipgrip utility so resources from PyPi get updated too
       brew 'install', 'pipgrip'
     end
 
@@ -144,6 +147,15 @@ def read_brew(*args)
       formula = info['formula']
       version = info['version']['latest']
 
+      # Get stable software spec of the formula
+      stable = Formula[formula].stable
+
+      # Check if formula is originating from PyPi
+      if !Formula["pipgrip"].any_version_installed? && PyPI.update_pypi_url(stable.url, version)
+        # Install pipgrip utility so resources from PyPi get updated too
+        brew 'install', 'pipgrip'
+      end
+
       begin
         # Finally bump the formula
         brew 'bump-formula-pr',