refactor(python): better handling of TREZOR_BLE flag

diff --git a/python/src/trezorlib/cli/__init__.py b/python/src/trezorlib/cli/__init__.py
index 1b1d8154..25efa9e6 100644
--- a/python/src/trezorlib/cli/__init__.py
+++ b/python/src/trezorlib/cli/__init__.py
@@ -139,13 +139,11 @@ class TrezorConnection:
         session_id: bytes | None,
         passphrase_on_host: bool,
         script: bool,
-        ble_enabled: bool,
     ) -> None:
         self.path = path
         self.session_id = session_id
         self.passphrase_on_host = passphrase_on_host
         self.script = script
-        self.ble_enabled = ble_enabled
 
     def get_session(
         self,
@@ -219,9 +217,7 @@ class TrezorConnection:
                 _TRANSPORT = None
         try:
             # look for transport without prefix search
-            _TRANSPORT = transport.get_transport(
-                self.path, prefix_search=False, ble_enabled=self.ble_enabled
-            )
+            _TRANSPORT = transport.get_transport(self.path, prefix_search=False)
         except Exception:
             # most likely not found. try again below.
             pass
@@ -229,9 +225,7 @@ class TrezorConnection:
         # look for transport with prefix search
         # if this fails, we want the exception to bubble up to the caller
         if not _TRANSPORT:
-            _TRANSPORT = transport.get_transport(
-                self.path, prefix_search=True, ble_enabled=self.ble_enabled
-            )
+            _TRANSPORT = transport.get_transport(self.path, prefix_search=True)
 
         _TRANSPORT.open()
         atexit.register(_TRANSPORT.close)
diff --git a/python/src/trezorlib/cli/trezorctl.py b/python/src/trezorlib/cli/trezorctl.py
index 4cf9bf58..0c0b220b 100755
--- a/python/src/trezorlib/cli/trezorctl.py
+++ b/python/src/trezorlib/cli/trezorctl.py
@@ -28,6 +28,7 @@ import click
 from .. import log, messages, protobuf
 from ..transport import DeviceIsBusy, enumerate_devices
 from ..transport.session import Session
+from ..transport.ble import BleTransport
 from ..transport.udp import UdpTransport
 from . import (
     AliasedGroup,
@@ -175,7 +176,6 @@ def configure_logging(verbose: int) -> None:
     "--ble/--no-ble",
     help="Enable/disable support for Bluetooth Low Energy.",
     is_flag=True,
-    default=(os.environ.get("TREZOR_BLE") == "1"),
 )
 @click.option("-v", "--verbose", count=True, help="Show communication messages.")
 @click.option(
@@ -210,7 +210,7 @@ def configure_logging(verbose: int) -> None:
 def cli_main(
     ctx: click.Context,
     path: str,
-    ble: bool,
+    ble: bool | None,
     verbose: int,
     is_json: bool,
     passphrase_on_host: bool,
@@ -220,6 +220,12 @@ def cli_main(
 ) -> None:
     configure_logging(verbose)
 
+    # if BLE was explicitly enabled, raise an error if it's not available
+    if ble and not BleTransport.ENABLED:
+        raise click.ClickException("BLE support is unavailable")
+
+    BleTransport.ENABLED = ble or (os.environ.get("TREZOR_BLE") == "1")
+
     bytes_session_id: Optional[bytes] = None
     if session_id is not None:
         try:
@@ -227,9 +233,7 @@ def cli_main(
         except ValueError:
             raise click.ClickException(f"Not a valid session id: {session_id}")
 
-    ctx.obj = TrezorConnection(
-        path, bytes_session_id, passphrase_on_host, script, ble_enabled=ble
-    )
+    ctx.obj = TrezorConnection(path, bytes_session_id, passphrase_on_host, script)
 
     # Optionally record the screen into a specified directory.
     if record:
@@ -303,13 +307,13 @@ def list_devices(
 ) -> Optional[Iterable["Transport"]]:
     """List connected Trezor devices."""
     if no_resolve:
-        for d in enumerate_devices(ble_enabled=obj.ble_enabled):
+        for d in enumerate_devices():
             click.echo(d.get_path())
         return
 
     from . import get_client
 
-    for transport in enumerate_devices(ble_enabled=obj.ble_enabled):
+    for transport in enumerate_devices():
         try:
             transport.open()
             client = get_client(transport)
diff --git a/python/src/trezorlib/transport/__init__.py b/python/src/trezorlib/transport/__init__.py
index 9cafde73..db2f2441 100644
--- a/python/src/trezorlib/transport/__init__.py
+++ b/python/src/trezorlib/transport/__init__.py
@@ -96,32 +96,28 @@ class Transport:
     CHUNK_SIZE: t.ClassVar[int | None]
 
 
-def all_transports(ble_enabled: bool | None = None) -> t.Iterable[t.Type["Transport"]]:
+def all_transports() -> t.Iterable[type[Transport]]:
     from .ble import BleTransport
     from .bridge import BridgeTransport
     from .hid import HidTransport
     from .udp import UdpTransport
     from .webusb import WebUsbTransport
 
-    transports: t.Tuple[t.Type["Transport"], ...] = (
+    transports: tuple[type[Transport], ...] = (
         BridgeTransport,
         HidTransport,
         UdpTransport,
         WebUsbTransport,
+        BleTransport,
     )
-    if ble_enabled is None:
-        ble_enabled = os.environ.get("TREZOR_BLE") == "1"
-    if ble_enabled:
-        transports += (BleTransport,)
     return set(t for t in transports if t.ENABLED)
 
 
 def enumerate_devices(
     models: t.Iterable[TrezorModel] | None = None,
-    ble_enabled: bool | None = None,
 ) -> t.Sequence[Transport]:
     devices: t.List[Transport] = []
-    for transport in all_transports(ble_enabled=ble_enabled):
+    for transport in all_transports():
         name = transport.__name__
         try:
             found = list(transport.enumerate(models))
@@ -135,14 +131,10 @@ def enumerate_devices(
     return devices
 
 
-def get_transport(
-    path: str | None = None,
-    prefix_search: bool = False,
-    ble_enabled: bool | None = None,
-) -> Transport:
+def get_transport(path: str | None = None, prefix_search: bool = False) -> Transport:
     if path is None:
         try:
-            return next(iter(enumerate_devices(ble_enabled=ble_enabled)))
+            return next(iter(enumerate_devices()))
         except StopIteration:
             raise TransportException("No Trezor device found") from None
 
@@ -157,11 +149,7 @@ def get_transport(
             "prefix" if prefix_search else "full path", path
         )
     )
-    transports = [
-        t
-        for t in all_transports(ble_enabled=ble_enabled)
-        if match_prefix(path, t.PATH_PREFIX)
-    ]
+    transports = [t for t in all_transports() if match_prefix(path, t.PATH_PREFIX)]
     if transports:
         return transports[0].find_by_path(path, prefix_search=prefix_search)
 
diff --git a/python/src/trezorlib/transport/ble.py b/python/src/trezorlib/transport/ble.py
index 5dd1f0b7..12c01d6f 100644
--- a/python/src/trezorlib/transport/ble.py
+++ b/python/src/trezorlib/transport/ble.py
@@ -53,7 +53,7 @@ SHUTDOWN_TIMEOUT_SECONDS = 10
 
 
 class BleTransport(Transport):
-    ENABLED = True
+    ENABLED = BLEAK_IMPORTED
     PATH_PREFIX = "ble"
     CHUNK_SIZE = 244
 
diff --git a/tests/conftest.py b/tests/conftest.py
index 6594e5a7..4b98c003 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -33,6 +33,7 @@ from trezorlib.debuglink import TrezorClientDebugLink as Client
 from trezorlib.device import apply_settings
 from trezorlib.device import wipe as wipe_device
 from trezorlib.transport import Timeout, enumerate_devices, get_transport
+from trezorlib.transport.ble import BleTransport
 from trezorlib.transport.thp.protocol_v1 import ProtocolV1Channel, UnexpectedMagicError
 
 # register rewrites before importing from local package
@@ -175,6 +176,9 @@ def _client_from_path(
 
 
 def _find_client(request: pytest.FixtureRequest, interact: bool) -> Client:
+    if os.environ.get("TREZOR_BLE") != "1":
+        BleTransport.ENABLED = False
+
     devices = enumerate_devices()
     for device in devices:
         return Client(device, auto_interact=not interact, open_transport=True)