Drop bottle in favour of a tiny hand-rolled "framework"

Turns out ycmd needs a tiny part of the whole framework specification
from PEP 3333.
Note that this does not fully conform to the specification, but it
mostly does.

Currently we are only handling POST and GET requests.
Support for middleware is limited. Inspired by Bottle plugins API, but
only `plugin.__call__` and `app.install` are implemented.
Error handling is also limited. Application needs to replace the default
error handler that *will* handle all errors.

.gitmodules

@@ -1,6 +1,3 @@
-[submodule "third_party/bottle"]
-	path = third_party/bottle
-	url = https://github.com/defnull/bottle
 [submodule "third_party/jedi"]
 	path = third_party/jedi_deps/jedi
 	url = https://github.com/davidhalter/jedi

requirements.txt

@@ -1,4 +1,3 @@
-bottle   >= 0.12.18
 regex    >= 2020.2.20
 jedi     >= 0.16.0
 watchdog >= 0.10.2

run_tests.py

@@ -17,14 +17,10 @@
 LIBCLANG_DIR = p.join( DIR_OF_THIRD_PARTY, 'clang', 'lib' )
 
 python_path = [
-  p.join( DIR_OF_THIRD_PARTY, 'bottle' ),
   p.join( DIR_OF_THIRD_PARTY, 'regex-build' ),
-  p.join( DIR_OF_THIRD_PARTY, 'frozendict' ),
   p.join( DIR_OF_THIRD_PARTY, 'jedi_deps', 'jedi' ),
   p.join( DIR_OF_THIRD_PARTY, 'jedi_deps', 'parso' ),
   p.join( DIR_OF_WATCHDOG_DEPS, 'watchdog', 'build', 'lib3' ),
-  p.join( DIR_OF_WATCHDOG_DEPS, 'pathtools' ),
-  p.join( DIR_OF_THIRD_PARTY, 'waitress' ),
 ]
 if os.environ.get( 'PYTHONPATH' ) is not None:
   python_path.append( os.environ[ 'PYTHONPATH' ] )

ycmd/__main__.py

@@ -36,19 +36,10 @@
 DIR_OF_REQUESTS_DEPS = os.path.join( DIR_OF_THIRD_PARTY, 'requests_deps' )
 sys.path[ 0:0 ] = [
     os.path.join( ROOT_DIR ),
-    os.path.join( DIR_OF_THIRD_PARTY, 'bottle' ),
     os.path.join( DIR_OF_THIRD_PARTY, 'regex-build' ),
-    os.path.join( DIR_OF_THIRD_PARTY, 'frozendict' ),
     os.path.join( DIR_OF_THIRD_PARTY, 'jedi_deps', 'jedi' ),
     os.path.join( DIR_OF_THIRD_PARTY, 'jedi_deps', 'parso' ),
-    os.path.join( DIR_OF_REQUESTS_DEPS, 'requests' ),
-    os.path.join( DIR_OF_REQUESTS_DEPS, 'chardet' ),
-    os.path.join( DIR_OF_REQUESTS_DEPS, 'certifi' ),
-    os.path.join( DIR_OF_REQUESTS_DEPS, 'idna' ),
-    os.path.join( DIR_OF_REQUESTS_DEPS, 'urllib3', 'src' ),
-    os.path.join( DIR_OF_WATCHDOG_DEPS, 'watchdog', 'build', 'lib3' ),
-    os.path.join( DIR_OF_WATCHDOG_DEPS, 'pathtools' ),
-    os.path.join( DIR_OF_THIRD_PARTY, 'waitress' ) ]
+    os.path.join( DIR_OF_WATCHDOG_DEPS, 'watchdog', 'build', 'lib3' ) ]
 sys.path.append( os.path.join( DIR_OF_THIRD_PARTY, 'jedi_deps', 'numpydoc' ) )
 
 import atexit
@@ -203,7 +194,6 @@ def Main():
                                     args.stderr,
                                     args.keep_logfiles )
   atexit.register( handlers.ServerCleanup )
-  handlers.app.uninstall( True )
   handlers.app.install( WatchdogPlugin( args.idle_suicide_seconds,
                                         args.check_interval_seconds ) )
   handlers.app.install( HmacPlugin( hmac_secret ) )