Minor updates to find git task

Author: stephan-gh

src/main/groovy/net/minecrell/gitpatcher/Git.groovy

@@ -95,7 +95,7 @@ class Git {
             if (type == String) {
                 setup(null, System.err)
                 execute()
-                return process.getInputStream().text
+                return process.inputStream.text
             }
         }
 

src/main/groovy/net/minecrell/gitpatcher/task/FindGitTask.groovy

@@ -36,7 +36,7 @@ class FindGitTask extends DefaultTask {
             def version = (git.version() as String).readLines().join(', ')
             logger.lifecycle("Using $version for patching submodule $submodule.")
         } catch (Throwable e) {
-            throw new AssertionError(
+            throw new UnsupportedOperationException(
                     'Failed to verify Git version. Make sure running the Gradle build in an environment where Git is in your PATH.', e);
         }
     }