use logging instead of prints (#499)

# What does this PR do?

This PR moves all print statements to use logging. Things changed:
- Had to add `await start_trace("sse_generator")` to server.py to
actually get tracing working. else was not seeing any logs
- If no telemetry provider is provided in the run.yaml, we will write to
stdout
- by default, the logs are going to be in JSON, but we expose an option
to configure to output in a human readable way.

llama_stack/distribution/build.py

@@ -4,14 +4,13 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
+import logging
 from enum import Enum
 from typing import List
 
 import pkg_resources
 from pydantic import BaseModel
 
-from termcolor import cprint
-
 from llama_stack.distribution.utils.exec import run_with_pty
 
 from llama_stack.distribution.datatypes import *  # noqa: F403
@@ -22,6 +21,8 @@ from llama_stack.distribution.distribution import get_provider_registry
 from llama_stack.distribution.utils.config_dirs import BUILDS_BASE_DIR
 
 
+log = logging.getLogger(__name__)
+
 # These are the dependencies needed by the distribution server.
 # `llama-stack` is automatically installed by the installation script.
 SERVER_DEPENDENCIES = [
@@ -89,12 +90,12 @@ def get_provider_dependencies(
 def print_pip_install_help(providers: Dict[str, List[Provider]]):
     normal_deps, special_deps = get_provider_dependencies(providers)
 
-    print(
+    log.info(
         f"Please install needed dependencies using the following commands:\n\n\tpip install {' '.join(normal_deps)}"
     )
     for special_dep in special_deps:
-        print(f"\tpip install {special_dep}")
-    print()
+        log.info(f"\tpip install {special_dep}")
+    log.info()
 
 
 def build_image(build_config: BuildConfig, build_file_path: Path):
@@ -133,9 +134,8 @@ def build_image(build_config: BuildConfig, build_file_path: Path):
 
     return_code = run_with_pty(args)
     if return_code != 0:
-        cprint(
+        log.error(
             f"Failed to build target {build_config.name} with return code {return_code}",
-            color="red",
         )
 
     return return_code